To be completely honest, a 40 gallon tank is much too large for a young ball python (and even most adults!). Part of the reason your having feeding problems is probably that tanks size.
A 15q tub will not cost you more than 10 dollars, and for the health of the snake it is worth it. You can put him back in a show tank after he's grown a bit, eaten regularly, and completely healed. Right now, listening to Becky is the best thing you could do for your animal.
My snake didn't eat for 4 months, I found out it was because of the 20g enclosure it was in. After getting it settled in a tub, it's easier to clean, manage, and the snake is 10x happier and feeding. All with Becky's help.
Good luck.