Done With The Crying - Parents of Estranged Adult Children: Help and Healing.

I recommend reading this book to help you cope and decide how to move forward.

I read it a few years ago, during a situation with my son. I am relieved we have since repaired the issue. But, your situation sounds different in that it has been dysfunctional for a long time. My heart goes out to you and all parents who have had to cope with this.