Hello, welcome to the forum, and I think we can help you out, but it's important that you get him under a very strong, adequate UVB tube immediately, as at 7-8 months old he doesn't have much longer to start reversing any of the damage the MBD has done. The key to stopping the progression of MBD, strengthening his bone density, and hopefully reversing as much as the physical damage/paralysis that is already done is getting a T5-strength UVB tube, at least 22" long, and that is at least a 10% or higher UVB (10.0 or higher) and allowing both this new 10% T5 UVB tube and his bright white basking bulb on for at least 13-14 hours every single day.
A lot of people don't realize that if a dragon has a calcium deficiency and the resulting MBD, it's usually not at all due to the dragon's diet or calcium supplementation at all, it's due to them being under inadequate
UVB light, having their
UVB light be obstructed by a mesh lid to the tank that is blocking 40% or more of the
UVB light, or a clear plastic cover on the tube fixture that is blocking 100% of the
UVB light, having the UVB tube too far away from the BAsking Spot/Platform (for a T8 strength tube it must be within at least 6", for a T5 strength it must be within at least 11"), or not replacing the UVB tube soon enough or not at all, based on the UVB decay rate of the tube (T8 tubes must be replaced once every 6 months, T5 every 12 months at most). Without adequate, strong
UVB light, a dragon cannot manufacture their own vitamin D3, and in-turn cannot absorb, process, or use ANY nutrition they take in from the food they eat or the calcium or multivitamin supplements they are given, they simply excrete everything. This is why they also tend to lose a lot of weight, as they are not absorbing any protein, fat, calories, vitamins, minerals, etc.
It's awesome that you ordered the Reptisun T5 Hood and UVB tube, however, as Cooper already mentioned, that package comes with a Reptisun 5.0 T5HO UVB tube, which is only a 5% UVB tube, and not at all adequate for a Bearded Dragon, but rather meant for Tropical Reptiles who do not need such strong, intense
UVB light. You'd have to have that Reptisun 5.0 T5HO UVB tube within at least 4" of your dragon's Basking Spot in order for him to get any adequate
UVB light, and that's way too close for a T5 strength tube, or any tube, as it will cause eye damage. Not to mention it's pretty much impossible to do so in the first place.
So you must order the same length of Reptisun 10.0 T5HO UVB tube, I don't know what length hood you got, but if you order just a tube on Amazon.com, you can get a 22" Reptisun 10.0 T5HO UVB tube for $24 shipped. That's probably the cheapest place. You can order all sizes of the 10.0 T5HO UVB tubes on Amazon.com for similar pricing, the 34", the 46", etc. So either return the entire package from wherever you ordered it and just order both a Reptisun 10.0 T5HO UVB tube and then a matching T5-rated fixture with a Metal Reflector on Amazon.com (you can buy a 22" 10.0 T5HO tube and a T5-rated 24" fixture for it on Amazon.com for around $50 shipped for both), or just order the correct length 10.0 T5HO UVB tube from Amazon.com now and then just sell the 5.0 tube on Craigslist, eBay, or whatever you want to do with it and just keep the ZooMed T5 hood, it is a very nice hood. Either way though, you need the 10% T5HO UVB tube immediately.
Also, be sure to mount the 10.0 T5HO UVB tube within at least 11" of his basking spot/platform, replace it every 10-12 months, and keep it on for at least 13-14 hours every single day. Be sure that there is no clear plastic safety cover on the ZooMed hood or any other T5-rated fixture you may buy, as they block 100% of the
UVB light (the ZooMed hood shouldn't have any covers on it, but you never know any more, I've seen stranger things lately). And then once he's under a 10.0 T5HO UVB tube that is mounted correctly (be sure to have his bright-white colored Basking Bulb right alongside the UVb tube, not end-to-end but rather right alongside each other, both over the Hot Side of the tank, and then move his Basking Spot/platform directly underneath both lights within the Hot Side of the tank, so that he gets both lights at the same time while basking. This is the closest way to replicate natural sunlight for him.
He should perk up in both appetite and activity level after a few days under the 10.0 T5HO UVB tube (the 5.0 tube will not have much effect unless you have it extremely close to him, just an FYI, also, the 5.0 UVB tubes have a much faster decay rate, so instead of having to replace the 10.0 T5HO UVB tube once every 10-12 months, the 5.0 must be replaced once every 6 months at most, usually people with Tropical Reptiles replace them between 3-6 months, however it's inadequate for your dragon anyway, so again, you need to get a 10% T5HO UVB tube immediately, can't stress this enough)...Hopefully he will soon start to show improvement in his movement as well, but he will not ever be 100%, unfortunately, but he can live a very happy, quality life if you are vigilant about his lighting, temperature zones, diet, and supplementation from now on...