Check out Cesar Milan's website:
http://www.dogpsychologycenter.com/.
He asserts that no dog is too far gone to be rehabilitated. We've watched many many of the episodes on the National Geographic channel and have our Tivo programmed to automatically record his program.
He also says that dogs live in the present and it is we who live in the past. Dogs will pick up on your energy and act out according to your body language and the energy you project. Cesar is very insightful when it comes to what sort of body language you are unconsciously using with your dog. He teaches his clients how to project the right energy to communicate that
you are in charge, not the dog. I've seen him rehabilitate many very vicious dogs on his show that have been abused. What he says is that it is the owner's habit of not letting go of the past of these abused dogs that makes them hard to handle. Also, people tend to treat small dogs as if they were human, which makes them slightly neurotic. Dogs want to have a strong leader. If you don't project that, then they feel they must try to take charge of everything, a burden that makes them anxious and aggressive.
It sounds like you used many of his techniques, but what makes him successful in rehabing a dog is his ability to read the owner's mental state and correct it, and his unwavering determination never to give up on the dogs until he has succeeded.
If you really want your dog back (and I'm not trying to push you), you might try getting in touch with Cesar and ask if there is anything he can do to help you. As I said, he never gives up in his quest to rehabilitate.