Dixie, I'm confident that if anyone can retrain him and bring him back to his potential, it will be you. I do hope these people are not just playing games with you, let them know this is not a game with you, that you mean business.
I just know these kids have teased him and caused these problems and the mom and dad are too busy to see that. You would think if he nipped the kid once they would be a little caucious about them playing take away the toy game.
I sure hope it all works out and you get him back, he deserves a better life than what he has had. I just can't believe people like that. After you pick him up they will be out looking for another dog probably, the cycle never ends.
Jackie