tnmom, I do want you to know that I empathize with your sitch. A lot of what you've written is very telling.
I do want to ask you, has your entire relationship with him been you steamrolling him?
You appear to be a very strong character. I do understand you are frustrated right now, but it seems like for the entire relationship with him, you have "directed" all things in the relationship. Your entire focus right now appears to be pushing your will and desire on him and how custody and visits with D4 will go.
Do you make the majority of the decisions around your custody and visitation with your teen kids and ex?