Your H is dilusional in saying that the next time we fight I'm leaving. Maybe it's the way the two of you fight, do you resort to name calling and blame? Could you fight calmly and just agree to disagree? Wait until H and "Skank Ho" have an argument, fantasy land can't be perfect forever. Maybe he is already getting $hit from her and taking it out on you, who knows. Just remain calm and work on your GAL goals.
As far as the threat of violence, that is completely unacceptable under any circumstances.
Whatever you decide, keep coming here to vent, look for advice or lurk on others threads. This is a great place!
