The kids, even when grown, are the hardest part of it all. My girls refuse to have anything to do with OW, and consequently their Dad, and OW is using it to further drive a wedge between them.
As tough as it was/is, be glad he and D are not cutting each other out of their lives. Believe me, I understand how you feel completely. OW keeps pushing herself on my grands by SS. Insisting they spend the night. DIL isn't comfortable with that at all.
Wish I could say something cheerier, but it is what it is.