In my experience, if an adult cat has a biting habit, then the cat has a biting habit. They don't "learn" well - just keep neosporin and bandaids handy. =)

The drool problem I think may be fixable by some minor facial surgery. I had a friend who's cat drooled all - the - time. She took him and they were able to do a little tuck to his lips or something and that helped keep the saliva in his mouth. So...I recommend asking your vet if there's anything that can be done.