Wow Bill, sounds like you are tying your best. And that you care about this dogs life.
I would get a pet behaviorist as soon as possible. Tomorrow! Hook up with a trainer too, so you can get two opinions at least, go for a another trainer if you think it fits better, and for three opinions on the dog.
What i concerns me about the dog is that it sounds like he goes in for quite the bite.. Not a warning bite.. What kind of muzzle are you using?
Keep him on leash at all times with a muzzle when anyone else is around. No bed, no couch, etc. Make sure he gets plenty of exercise and mind stimulation.
Every time he is about to bite, he freezes up and stares at them. You have to be the interrupter to that train of thought in his head and what follows, if there is anyone who is going to be hurt, its going to have to be you- since he is your dog. How long does he stare at them and freeze before biting? Even a few seconds is enough for you to be quick in reaction time to be an interrupter.
Sounds like he is trying to control his space, if he is fearful that would make sense too.
But definitely get that trainer and behaviorist in as soon as you can! Hard core management for now!
Good luck! And remember that you are giving this dog, what no one else would. Your are giving him another chance. If you have to be the one to make that hard decision on his life, remember that. Makes you wonder what this poor dog wen't through, what kind of poor genetics he has too.. Poor kiddo