As much as I hate saying it, put him down. I have voluteered at a local dog pound that euthanises a lot of animals. We have a dog from them, a 5 year old black setter long haired mutt. If we wouldn't have fostered and adopted him, he would have been put down. But he is like the best dog ever. Protects my birds from predators, barks when intruders comes, but would never hurt anyone, if you call him he comes and rolls over and looks all cute, and is very calm and loves to go down to the creek and swim. So if a dog like ours was going to be put down, then that crazy thing sure should. You are doing the right thing.