Is either a family therapy session [all 5 of you] or a therapy session with your stbx and yourself and son 17 a possibility?
It sounds like you need to have an arena to talk openly but with another person there. Good therapists are hard to fool, and since both of the other 2 have self esteem issues they feel good about themselves by dissing you.
You will probably have to take this at first while they get it off their chests. Truth, to many people, is much less important than how they feel. Your son is upset with his mother I suspect, at bottom, but because he is closer to her he is blaming you. easier that way - saves having to think about the facts.
