I definitely don't think he's an adult... unless he was really poorly kept? I have never seen such poor horn growth in an adult male. He has too long of horns for sure for him to be female. Can you get a picture more of his face? His legs worry me a bit, not with bone disease or anything, but just how skinny they are. Jackson's have relatively chubby legs compared to most species around the same size. Do you know his measurements in length? Or his weight in grams at all? I wouldn't expect him to eat right away, that's pretty normal. Do you know for certain he is wild caught or captive bred? How long are your misting him for? What are your basking temps?