If you have the means, run to a lawyer to explore your options. Much of this depends on what court you can get to hear it. Your son needs counseling as well. She is using him for her emotional support system.
Have you called the school he is at to ask if they have a counselor through the school to at least start a dialogue with him?
Give it some time and I know some of the other posters will probably weigh in with their thoughts as wel.