I wonder if he was wild caught. Did the last owner say? BPs that are wild caught can be a nightmare to feed, and probably shouldn't be bought by first time snake owners.
Its very strange to have a ball python become aggressive (if bred in captivity) They are generally very docile. You are either doing something very wrong, or the snake is sick. Or maybe he just wasn't handled enough by his past owner to get tame.
The trouble with snakes is, when they snap once, and you back off, they learn they can bite to get what they want. If he does snap at you or bite you, don't back down. Pick him up and handle him and show him you're not afraid. He bites because he knows it gets him what he wants. If he snaps at you, do NOT put him down immediately. Carry on as if nothing happened. He'll soon learn. And don't be freaked out; it barely pinches.
The amount of feeding has absolutely nothing to do with his temperment, so get that outta your head.
I would also suggest putting two hides in the tank... one near the heat, and one on the other side of the tank on the cool side. Ball pythons are very very shy, and they'll ignore their basic heating needs in favor of feeling 'safe.' Try different things like introducing him to the hide by moving his head into the hole and seeing if he's interested. Move the hides around, and switch to a different type of hide (make sure they're refundable.... otherwise this could get expensive. Or make one out of a plant pot turned upside down with a hole cut into the side. They like small spaces.)
The best thing you could possibly do for your snake right now is learn more about it. It's going to suck, but go on google and look up 'ball python husbandry' and read every single article on that page, until you're so sick of it you're about to yank your eyeballs out.
You'll figure out what you're doing wrong eventually. None of us on Y!A can really tell you, because we arent there. The main thing though is handling your snake no matter what.. remember... show no fear or this will escalate. Don't let the snake boss you around. If he isn't tame, you have to do this to tame him.
Good luck.