this statement "Now that he is able to decide if he wants to be at our house--dh has joint legal, eow, 2days during week and we live 20 miles apart with us doing all the driving--he has said numerous times that he wants to come live with us." and throughout your post you indicate that your
SS has the power to make these decisions.
Let me tell you, he does not. He is still a child and should not have the ability to play one household against the other, which is what he seems to be doing.
I would focus on him and his schoolwork, and try to make a difference there - get involved as much as possible. Get him a counselor to talk to.
Skids living with you can sound wonderful but most often leads to many many more problems, if the kid is screwed up. Be careful what you wish for!