I'm so sorry you have so much serious stuff to think about
My thoughts after reading your post are....
As a parent I've told my children I will always believe them. They can tell me anything and I will believe them. You don't have to figure it all out on your own. Your daughter requested counseling and I'd jump on that excellent idea.
There are three 'rules' in an alcoholic home. Do not trust, do not talk, do not feel. Your daughter is doing her own recovery and she has offered you a valuable gift with the request for counseling.
You've filed for divorce. Your lawyer can tell him or his lawyer that all communication will go through him from now on and then delete every message he sends before listening to it. That is what I would do.