Start reading everything here...
https://chameleonacademy.com/chameleon-husbandry-program-getting-started-with-chameleons/
But to turn this around you need an enclosure change. needs to be upgraded to a 2x2x4ft size enclosure. He can not be in the tiny cage. There is not enough room to move around or regulate temps in the little cage.
And you have to upgrade to a T5HO 24 inch fixture and a 5.0 or 6% uvb bulb. What you are using now will not work for UVB. You would use this fixture sitting on top of the new cage and then have 8-9 inches of space between it and the closest branches to have the right uvb level.
Supplements should be calcium without D3 at all feedings and then a multivitamin like Reptivite with D3 only 2 times a month say the 1st and the 15th.
His body is starting to shut down. This is a combo of incorrect UVB lighting and D3 overdose. You can turn this around but you have to make changes very quickly. This link above will teach you how and then ask your questions here.