Keep the water tip top and keep an eye on him, he's been trough a lot, swimbladder damage and new tank, so maybe he just needs time to adjust. drop a bit of food in and if he doesn't eat it in 10 mins take it back out and try again the next day.
There is a chance he has had more injury than we first thought, but time will tell. The hump will go down when he has nothing to display to