He is already used to that language. I stick with it. I incorporate hand and voice both in the training. No, I don't use code words just their language. Yes, they have to learn the commands that the dogs are taught in.
Abuse is a tough question.
That is something for the experts to see and evaluate. Take the dog to a local trainer. It is part game and part reaction to a comand. They go without any major training. Don't start with a dog that has neither the talent or the courage to begin with.