Agree with Britster. You already have the answer. If necessary, get a soft muzzle to protect yourself from bites when working on nails. It's time for
you to get strict again & help him relearn proper behavior. It's time for
you to let go of the unfortunate surgery. It may take time & patience, but since the surgery, he's been allowed to have everything his way, giving him a whole lot of power over the family. Good luck!