Okay, you've got some serious issues, first with your
UVB light. First of all, unless it's a T5 High-Output UVB tube it cannot sit on top of any mesh or glass, he's gotten zero UVB. Also, depending on what exact UVB tube you have, it must not only be mounted inside his enclosure, but it has to be the correct distance from your beardie when he sits on his basking spot, usually between 6-8" unobstructed. And if your UVB tube fixture has any clear plastic cover over the tube, it's also blocking the
UVB light from getting through, and needs removed. And if your tube is older than 6 months it no longer emits
UVB light and you must replace it immediately. But first, you need to read what is written on the tube itself, it will say the brand and model/wattage. My guess is that it's not an Arcadia or a Reptisun, so it's not an adequate UVB tube for a bearded dragon anyway, and then it's been instructed by the mesh lid and possibly a clear plastic cover on the fixture. So your beardie has gotten no UVB. It's quite obvious that he is suffering from severe MBD, he is badly stunted and half the size he should be, but more importantly his head and bone structure is showing deformities like the severe underbite and the paralysis in his back legs. He needs a proper UVB tube mounted inside his tank at the proper height, unobstructed by anything between him and the tube. This will not only allow him to process his Calcium and increase his bone density, but it will up his appetite. It either needs to be an Arcadia 12% UVB tube, or a Reptisun 10.0 T5 High-Output UVB tube, I'd skip the T8 tube because he needs the stronger UVB right now.
Now the second problem is your temperature gradient. You do not have an adequate thermometer. Those round gauge thermometers are often off by up to 20 degrees, a d you have no way of measuring his basking spot temperature, which is the most important temp. You need to go out and buy a digital thermometer that has a probe on a wire, so that you can place the probe on his basking spot where he sits, let it sit for 20-30 minutes, then read the temperature. Then move the probe off of the basking spot down to the floor surrounding it on that end of the tank, let it sit for 20-30 minutes, and read the temperature. This is his Hot Side. Then move the probe to the entire other end of the tank, lay it on the floor for 20-30 minutes, and read the temperature. This is the Cool Side. The temps inside his tank must be within the following ranges for him to be able to properly digest his food, absorb nutrients, be able to cool down, etc.
Cool Side: 75-80 degrees Fahrenheit maximum
Hot Side: 88-93 degrees Fahrenheit maximum
Basking Spot: 100-105 (at 11 months he will want it cooler than the 105-110 basking spot range that babies and juveniles do, that's why he's mouth gaping, if he's gaping it's too hot)
Remove the red night light, no lights on at night at all, his night temperature must drop like it does in the wild. As long as the temp is at least 65 degrees Fahrenheit he needs no heat source.
He needs Calcium every single day and a multivitamin 5 days a week for now, but honestly he needs to see a certified reptile vet immediately and get a calcium injection, and he should be on liquid Calcium daily for a while. His bone density is non-existent right now, which is both dangerous and effecting every part of his body functions. Until you get a proper UVB tube mounted inside the tank at the correct distance from the basking spot, and you get his temperature gradient correct, he will not be able to absorb any of the Calcium you give him, any nutrition from his food, nor be able to properly digest anything. His appetite is being heavily effected by the lack of
UVB light and the incorrect temperatures. He's a very sick little beardie, and whether or not he regains the use of his legs completely or he is able to gain some size and weight is completely dependent on you getting him the proper UVB tube and correct temperatures, and getting them both mounted right alongside each other and the UVB at the correct distance ASAP. The sooner you do this, the better chance he has to survive and maybe reverse some of the effects of the MBD, but it's really pretty bad, I'm sorry.
