When I dog bites hard enough to puncture, you NEED professional help. Failing that, I recently posted nothing in life is free. You need to get to it immediately. Stop raising your voice, but make him work for every single bite that goes in his mouth. No furniture, no bed, his place is his crate.
He doesn't KNOW he's in trouble, he knows you are trying to correct him and his response is PRECISELY what an alpha does to underlings… he bites. You need to have a plastic baseball bat, the soft ones or very light, so that when you tell him to get off the bed or furniture, IN AN EMERGENCY (as in if he rushes you) you can keep him off.
However, I would avoid corrections and work on limiting his access to anywhere in the house except his crate. Out of crate, have him on a leash long enough to let him move around but so you CONTROL HIM ALL THE TIME. Food? sit, down, sit down, whatever.. he works for every single bit that goes in his mouth. Keeping him leashed will help prevent you getting bit because you have control of him.
Because here is the bottom line. You can't "give him up." No one can take him and you can't afford to let them. If he bites someone, with you knowing he bites, they can sue you. Either you fix this, or you do the responsible thing, take him to your vet, and put him down.
I work with aggression issues, and I wish to heck we were closer, but right now, you have to prevent any more bites and you have to stop the behavior.
As for thyroid, unless the panel was sent to somewhere really reputable (I insist on Michigan), have it redone. I see people praise Dodds and I don't want to get into a debate about her... but I know many people who had dogs who were triple tested that SHE said had major thyroid problems that no one else found. It is her "thing." So use one of the OFA approved labs. And if the result is EVEN borderline, get your vet to put him on a low dose to see if it helps.
Ditto on neutering... it helps some, but you still have to work directly on this issue.
But understand even if thyroid, this dog have now established a behavior and that behavior MUST be stopped. When he backed you off the first time, he began to see that as an option. He must rethink it. He must learn you are in control and you can tell him no.. no firmly, just use your normal voice.
