Oh I'm sorry he's seemingly getting worse, but I agree with Tracie, I think he was overheated and dehydrated for quite a while, plus as you said he had no UV at all prior to coming home with you, and Dragons are very effected physically by stress, their immune systems seem to break down when they are stressed and his parasite counts (Coccidia most likely) has probably gone up from zero or low to moderate to high. This combined with no nutrition and the dehydration causes a downward spiral.
His arms being "tucked into his sides" all the time does sound like an MBD symptom, they often fold their front legs together or underneath themselves with MBD. How are his back legs working? Is he at all dragging them or having trouble with bowel movements? And speaking of bowel movements, when was the last time he had one? Realize that "No Food In=No Food Out", but if he's getting liquids/baby food he should still be excreting something. I'm just worried about a possible impaction, that's always a possibility with very small, young babies too, especially with a possibility of MBD, sometimes they lose the strength in their back end and seem to "strain" to even pass liquids.
Right now the main goal is to try to get as much nutrition and hydration in him as possible. Small amounts frequently throughout the day are much better than large amounts all at one time. Feeding him baby foods that have a higher protein/calorie/fat content is best, the one that I found recently that not only has an unusually high calorie/protein content was a $0.60 little jar, Gerber brand, and it is "Sweet Potato Corn". (My 6 month old recently had a very high Pinworm count and stopped eating). He really likes the Sweet Potato, so while looking for it at Walmart I was reading labels to find the one with the most calories/protein/fat, and after reading dozens of labels, the "Sweet Potato Corn" had the most calories/protein/fat, even much more than any of the meat flavors, surprisingly. He liked it too.
I would also buy some unflavored Pedialyte (or the generic store brand) and add it to the baby food to help get him extra electrolytes. I use the unflavored Pedialyte to thin pretty much anything I'm force-feeding. It really seems to perk them right up within minutes of taking it.
I'm also glad that you got a 24" Reptisun UVB tube and that you have it mounted underneath the mesh lid...Is it the weaker T8-strength or the stronger T5HO-strength? Either is good, you just have to make sure that if it's the weaker T8-strength that he can get within at least 6" of it (as opposed to within at least 11" of the stronger T5HO), because if it's any further away from him he won't be able to get adequate UVB light from it. The UVB tubes don't get hot like the basking bulbs or the CHE's, so no need to worry about him burning himself on the UVB tube. Also, just as an FYI, the T8 tubes must be replaced once every 6 months, the T5HO tubes once every year.
If you're having trouble force-feeding him (it can be very stressful for both you and him) you can try the folded-cardboard method that Tracie explained, it works well for some dragons, but I also have my own method that I find very easy and much less stressful than a lot of other methods of force-feeding that you can try...
I don't know what you're using to force-feed him with, but for my method you simply need either an oral syringe that has a tip on it, or a disposable "Leur-Slip" syringe that you can buy at any Tractor Supply very cheaply, a box of 6 Leur-Slip syringes (without needles of course) that are the 3ml volume costs a little over $2 at Tractor Supply. They have other volumes, that really doesn't matter, but since I usually force feed 3ml at a time, I buy the 3ml ones. And not only are the Leur-Slip syringes cheap, but I find that they have a longer tip than most Oral Syringes do, I guess because they are meant for a needle to "slip over and onto the tip", so they have a longer tip. And the tips on the Leur-Slip syringes seem to also be much skinnier than the tips on most oral syringes, so they work better for small babies. Either with work though, just don't confuse the Leur-Slip syringes with the "Leur-Lock" syringes that Tractor Supply also sells in the same section, as the "Leur-Lock" syringes do not have any tip at all, they have an internal locking system for the needles to attach to, so they don't work at all for force-feeding.
So here's what I do: First of all, I always add a pinch of their Calcium powder to the slurries, and also a very small pinch of their multivitamin powder to them as well. I also always heat the slurries up in the microwave, so I mix them in a little microwave-safe container, and then nuke them for 30 seconds, mix very well, and then nuke for another 30 seconds. Remove from the microwave and then mix again extremely well (you don't want any hot-pockets of slurry). Then I fill the syringe I'm using and test a little on my wrist, just like you would test a baby's bottle. You want the slurry to be warm, but not hot.
So this is the easiest and least stressful way I've found to force-feed a dragon liquids/slurries when you need to get more nutrition and/or hydration in them than you can just by dripping it on their snouts. After you do this a few times it becomes very easy, and even the dragon gets the hang of it. They won't "like it", lol, but it won't hurt them or scare them. So fill your syringe with the amount of slurry you'll be giving him (so you don't have to stop and refill all the time), and then put the dragon on a flat surface in front of you. You're going to hold him with your non-dominant hand, and then work the syringe with your dominant hand. Start by inserting the tip of the syringe under the dragon's upper lip, on the SIDE of his mouth/head, back towards his ear. Once you get the tip of the syringe under his upper lip on the side of his mouth/head, slowly slide the tip of the syringe up his mouth and towards the tip of his snout, keeping the tip of the syringe under his upper lip the entire time. Be ready with your thumb on the plunger of the syringe while you're sliding the tip up his mouth. For whatever reason (I really don't know why, but it seems to always be true) once the tip of the syringe nears the front of his mouth/tip of his snout, the dragon will automatically open up his mouth. As soon as he opens up his mouth the tip of the syringe will typically fall into his mouth and end up in-between his teeth (like he's chewing on the tip of the syringe, which he probably will actually start to do), if the tip of the syringe doesn't automatically end up inside his mouth, when he opens his mouth just put the tip in between his teeth, this will keep him from shutting his mouth, and then gently and slowly push a small amount of the slurry into his mouth. You'll see him making "chewing" and "swallowing" motions, after they stop then push a little more slurry in, allow him to swallow it, then push a little more in, etc. Continue to do this until you get the entire amount of the slurry in him. Keeping the tip of the syringe in-between his teeth will keep his mouth from shutting, but if for some reason the tip comes out from between his teeth and he does get his mouth shut, you'll need to start over again, by putting the tip of the syringe under his upper lip, back on the side of his mouth/head, and then again slide the tip of the syringe up the side of his mouth towards the tip of his snout, until he again opens his mouth, and then repeat. After you do this once or twice you'll get the hang of it. It's the quickest, easiest way I've found to force-feed a dragon...
His arms being "tucked into his sides" all the time does sound like an MBD symptom, they often fold their front legs together or underneath themselves with MBD. How are his back legs working? Is he at all dragging them or having trouble with bowel movements? And speaking of bowel movements, when was the last time he had one? Realize that "No Food In=No Food Out", but if he's getting liquids/baby food he should still be excreting something. I'm just worried about a possible impaction, that's always a possibility with very small, young babies too, especially with a possibility of MBD, sometimes they lose the strength in their back end and seem to "strain" to even pass liquids.
Right now the main goal is to try to get as much nutrition and hydration in him as possible. Small amounts frequently throughout the day are much better than large amounts all at one time. Feeding him baby foods that have a higher protein/calorie/fat content is best, the one that I found recently that not only has an unusually high calorie/protein content was a $0.60 little jar, Gerber brand, and it is "Sweet Potato Corn". (My 6 month old recently had a very high Pinworm count and stopped eating). He really likes the Sweet Potato, so while looking for it at Walmart I was reading labels to find the one with the most calories/protein/fat, and after reading dozens of labels, the "Sweet Potato Corn" had the most calories/protein/fat, even much more than any of the meat flavors, surprisingly. He liked it too.
I would also buy some unflavored Pedialyte (or the generic store brand) and add it to the baby food to help get him extra electrolytes. I use the unflavored Pedialyte to thin pretty much anything I'm force-feeding. It really seems to perk them right up within minutes of taking it.
I'm also glad that you got a 24" Reptisun UVB tube and that you have it mounted underneath the mesh lid...Is it the weaker T8-strength or the stronger T5HO-strength? Either is good, you just have to make sure that if it's the weaker T8-strength that he can get within at least 6" of it (as opposed to within at least 11" of the stronger T5HO), because if it's any further away from him he won't be able to get adequate UVB light from it. The UVB tubes don't get hot like the basking bulbs or the CHE's, so no need to worry about him burning himself on the UVB tube. Also, just as an FYI, the T8 tubes must be replaced once every 6 months, the T5HO tubes once every year.
If you're having trouble force-feeding him (it can be very stressful for both you and him) you can try the folded-cardboard method that Tracie explained, it works well for some dragons, but I also have my own method that I find very easy and much less stressful than a lot of other methods of force-feeding that you can try...
I don't know what you're using to force-feed him with, but for my method you simply need either an oral syringe that has a tip on it, or a disposable "Leur-Slip" syringe that you can buy at any Tractor Supply very cheaply, a box of 6 Leur-Slip syringes (without needles of course) that are the 3ml volume costs a little over $2 at Tractor Supply. They have other volumes, that really doesn't matter, but since I usually force feed 3ml at a time, I buy the 3ml ones. And not only are the Leur-Slip syringes cheap, but I find that they have a longer tip than most Oral Syringes do, I guess because they are meant for a needle to "slip over and onto the tip", so they have a longer tip. And the tips on the Leur-Slip syringes seem to also be much skinnier than the tips on most oral syringes, so they work better for small babies. Either with work though, just don't confuse the Leur-Slip syringes with the "Leur-Lock" syringes that Tractor Supply also sells in the same section, as the "Leur-Lock" syringes do not have any tip at all, they have an internal locking system for the needles to attach to, so they don't work at all for force-feeding.
So here's what I do: First of all, I always add a pinch of their Calcium powder to the slurries, and also a very small pinch of their multivitamin powder to them as well. I also always heat the slurries up in the microwave, so I mix them in a little microwave-safe container, and then nuke them for 30 seconds, mix very well, and then nuke for another 30 seconds. Remove from the microwave and then mix again extremely well (you don't want any hot-pockets of slurry). Then I fill the syringe I'm using and test a little on my wrist, just like you would test a baby's bottle. You want the slurry to be warm, but not hot.
So this is the easiest and least stressful way I've found to force-feed a dragon liquids/slurries when you need to get more nutrition and/or hydration in them than you can just by dripping it on their snouts. After you do this a few times it becomes very easy, and even the dragon gets the hang of it. They won't "like it", lol, but it won't hurt them or scare them. So fill your syringe with the amount of slurry you'll be giving him (so you don't have to stop and refill all the time), and then put the dragon on a flat surface in front of you. You're going to hold him with your non-dominant hand, and then work the syringe with your dominant hand. Start by inserting the tip of the syringe under the dragon's upper lip, on the SIDE of his mouth/head, back towards his ear. Once you get the tip of the syringe under his upper lip on the side of his mouth/head, slowly slide the tip of the syringe up his mouth and towards the tip of his snout, keeping the tip of the syringe under his upper lip the entire time. Be ready with your thumb on the plunger of the syringe while you're sliding the tip up his mouth. For whatever reason (I really don't know why, but it seems to always be true) once the tip of the syringe nears the front of his mouth/tip of his snout, the dragon will automatically open up his mouth. As soon as he opens up his mouth the tip of the syringe will typically fall into his mouth and end up in-between his teeth (like he's chewing on the tip of the syringe, which he probably will actually start to do), if the tip of the syringe doesn't automatically end up inside his mouth, when he opens his mouth just put the tip in between his teeth, this will keep him from shutting his mouth, and then gently and slowly push a small amount of the slurry into his mouth. You'll see him making "chewing" and "swallowing" motions, after they stop then push a little more slurry in, allow him to swallow it, then push a little more in, etc. Continue to do this until you get the entire amount of the slurry in him. Keeping the tip of the syringe in-between his teeth will keep his mouth from shutting, but if for some reason the tip comes out from between his teeth and he does get his mouth shut, you'll need to start over again, by putting the tip of the syringe under his upper lip, back on the side of his mouth/head, and then again slide the tip of the syringe up the side of his mouth towards the tip of his snout, until he again opens his mouth, and then repeat. After you do this once or twice you'll get the hang of it. It's the quickest, easiest way I've found to force-feed a dragon...