Yes, he definitely has MBD, but "Upping his Calcium Intake" isn't going to help him at all without an adequate
UVB light that is mounted correctly, and actually giving him extra Calcium without an adequate
UVB light can actually cause more issues for him. You must get him an adequate
UVb light ASAP or the MBD is going to only get much, much worse until he cannot walk at all. He's also quite thin, and this too is due to not having any
UVB light. He is a desert reptile and they need at least, at the very least 13-14 hours every single day of adequate
UVB light and a bright white Basking light together. Your compact/coil
UVB light is far too weak for a Bearded Dragon to begin with, and then the mesh lid is blocking about 40% of the already far too weak
UVB light. In addition, those weak compact/coil UVB bulbs also stop emitting ANY
UVB light at all at 6 months old. The bulb will still turn on and light up, but all of the
UVb light decays away at 6 months old. So he's gotten no
UVb light at all for however long you've had him, and this has caused severe MBD and an appetite problem, and probably also a malnutrition issue.
Here's why upping his Calcium won't help at all, and also why he's thin and malnourished: Desert Reptiles obviously get bright, intense, natural sunlight all day long, every day. As such, their bodies rely upon the different spectrum of light in order to pretty much do anything at all, including live.
Bearded Dragons need at least 13-14 hours every single day of adequate and strong
UVB light. Without this, their bodies stop making any Vitamin D3 and stop absorbing ANY of the nutrition that they eat, including Calcium and all other vitamins and minerals. They also cannot use/process any nutrition that they eat, not in supplement form or contained in their food. So if you feed him an adequate daily diet and give him a Calcium supplement and a Multivitamin supplement but he has no adequate
UVB light, he's just going to excrete all of the vitamins and minerals he takes in, including the calcium. This results in weakening of his bone density, deformities, paralysis, a lack of appetite, malnutrition, and eventually death.
So the bottom line here is that you absolutely must find a way to get him an adequate UVB tube (a long tube, at least 18" long, not another compact/coil
UVb bulb, as they are not going to help him), and a matching length, long tube fixture for the UVb tube. Your dragon needs a T5-strength UVB tube and fixture, because it is the strongest
UVb light you can buy, and also because you'll save money in the long run, which is something most people don't realize. If you buy a much weaker T8 UVB tube and fixture, you'll have to be replacing the T8 UVb tube at least once every 6 months, because they stop emitting any
UVb light at that age. Also, the T8 UVB tubes have to be mounted underneath the mesh lid, but the stronger T5 UVb tubes can sit on top of the mesh lid, just as long as his basking spot/platform is within at least 11" of the T5 UVB tube....in contrast, the weaker T8 UVB tubes have to be within at least 6" of his basking spot/platform to get effective
UVb light to him. So the T5 UVb tubes not only give him the best chance for survival and some recovery from this severe MBD and malnutrition, but the T5 UVB tube will save you money too (they actually cost less on Amazon.com than the weaker T8 UVb tubes do in the stores, by far), and are also easier to mount and get set-up properly.
You need to come up with $50 that you can use to order a 22" Reptisun 10.0 T5 High-Output UVB tube ($23 on Amazon.com) and then also a 24" T5-rated tube fixture with a Metal Reflector inside it ($25 on Amazon.com)...this is the cheapest place by far to buy both the UVB tube he needs and the long tube fixture for the UVB tube (the metal reflector is very important). Amazon.com offers a package deal when you buy both the UVb tube and the fixture together, and they offer free shipping. If you were to buy a 22" Reptisun 10.0 T5HO UVb tube in a store (if you could even find one, usually all they sell are the much weaker T8 versions) the tube alone would cost you $40. Then a 24" tube fixture that is rated for a T5 UVb tube (24 watts) would cost another $30 or so. So that's why Amazon.com is by far the best place to buy this for him.
So if you can come up with $50 you can get him both an adequate and easily set-up UVB tube and a fixture for it. Without a long, UVB tube (either a Reptisun 10.0 or an Arcadia brand, stay away from All Living Things, Zilla, and ReptileOne brands, they emit harmful light rays that cause eye and neurological damage, and they are very weak T8 UVB tubes that decay in less than 6 months and must all be mounted extremely close to your dragon at all times to deliver any effective
UVb light)...
Without getting him a long UVB tube and fixture and getting it set-up correctly ASAP, he's not going to get better, no matter what you do (unless you live somewhere where it's warm all year-round, then you can take him outside for a couple hours every day for direct sunlight).