Hello and Happy Friday. Your son could benefit from counseling tremendously. If he will not go to a counselor at a medical facility, then speak with his school's psychologist once school starts and explain the situation with your son. The psychologist can meet with him during school time. He will have no choice but to meet then. Also, if it is at a public school the services will be free (at least they should be).
Your son probably has a great deal of repressed anger issues about the divorce and probably blames you. It might be better if he were to live with his dad to see if his behavior and attitude would change but dad would have to be strict and not let him be disrespectful and provide activities in which he could socialize more.
Playing computer games all day long is awful. The violence on those games is almost like one is in Iraq. Sitting in one's room all day and interacting on that manner is not healthy at all. I would take the X Box and computer out of his room for a while as a punishment for his behavior. he will be upset but he must show you and the rest of the family more respect.
I think counseling would be the route to go. No teen ager ever wants to go see a counselor because they feel it is for "crazy "people. But to start if he will not go, then you should seek counseling for your sanity to learn intervention and coping strategies in dealing with your son.
Have a great day.