Hi there... new here but just read your post... sorry for that situation. You seem to be tho pretty clear now that you will separate, I guess he has shown you his real face ... I am in a similar situation, 2 weeks ago only I moved out. He is making some lame efforts to communicate but really cannot. He just wants to see us as a family and does not really care about my feelings. I know it is all about the kids. But I can tell you that your ex is hiding behind his kids too.... that is one way never to grow up!
Hoping you find a base of communication with him. I am reading the book “Uncoupling” for the second time already.... see if it would help you. You seem to be a nice person who wants the kids to have relationship w the grandparents etc. I loved the book... all the best to you... one step at a time. Xo. Big hug