Not to mention that if the UV bulb being used was older than six months, the little guy may not have been getting ANY benefit from it at all. All sorts of things could have contributed to this, none of them your fault.
You should really have a heart to heart with the breeder though, she sold...
I will strongly agree that that looks like MBD. Chameleons tend to sit in that position, and I don't think I've seen any of mine look rubbery like that, in any position. Clearly it isn't YOUR fault, since you just got him, but I would second guess the breeder. Also, as Royden suggested, take...
I'm with everyone else. Far too hot, he will cook at those temperatures.
Cute little guy though! He will love his life in that big reptarium! Just be sure that you cup feed so he has easy access to his food.