He definitely has some bone density/calcium/phosphorus issues. The "collapsed" spinal posture and bent legs are give aways. You can improve his life a lot though. He may not ever look totally normal as the bones will heal as they are, but he may not get any worse with better lighting (don't believe the claims on most reptile lights...they don't stand up to independent testing usually) and feeding. Getting outdoors in real sun is great...when the weather permits, but you probably won't be able to do this year round. The ReptiSun 5.0 is consistently best and safest for eyes. Good quality gutloading his insects is important too. Give his feeders fresh leafy greens, fruit and veggies (not broccoli or spinach), fortified cereal grains, bee pollen. Most commercial insect gutloads sold in pet shops are pretty terrible.
Some additional calcium from a vet will help initially, but you can overdose it too. Get him better light, better gutloading, correct calcium dusting and occasional vitamin dusting on a schedule for the longer term so you don't go too far overboard. I haven't treated a cham for calcium deficiency in a long time so am not an expert on current treatments for it.