Actually, I think your last idea is an interesting one. When my W was planning an ill-timed (for a bunch of reasons) girls weekend with her new "grass is greener" recently divorced bff, every bone in my body wanted her to not do it. My first instinct was to tell her why she couldn't go, then follow it with subtle comments noting my disapproval (my typical M.O. in those situations) but my IC advised me to do the opposite and tell her "wow, that sounds like fun, go and don't worry about a thing at home." Caught her off guard for sure. The tough thing was sticking to that philosophy, including during that weekend when she was gone, but I was glad later that I did.
IDK, in your case my first instinct would be to individually confront her dad and lay down the boundaries that I expect and make clear what I am willing to do to protect my family, so that we are clear. But, I think that is likely to have the opposite effect in your situation given where things are. And, that is an instinct, doesn't mean it is a smart idea.
Sorry for thinking as I type this, but what about saying that you are happy for your D that he is coming but calmly tell her that you have some boundaries, explain them, and if he crosses them, don't expect you to sit by quietly and not confront him? For example, if he insults you, your D, or your W, you are going to say something back?
Have you and her "dad" ever talked one on one since this started?
Me; 42, W; 43 M; 16 yrs S12, D9
3/13 - "I want to move to XYZ City (four hours away) and it might be without you, not sure" 5/13 - "Not sure I meant that"