OneArt,
I am begining year 9 of this. I cut all contact on my end for a very long time . He pokes at me directly from time to time.
He uses the kids to get a reaction from me. Him and Son got into an arguement while i was moving D18 to North Bay.
D15 has been told 3 weeks ago that he would get her phone fixed. Last week, he told her it would get done in the coming days. Yesterday, he told her it would be done today. Her phone still ain' t working and he gives her sh**t for not answering his text.. hello?? Her phone is broken.. the account is under his name and they will not let us deal with it.

Last week-end, he visited D18. He was hedgy and snappy all week-end and has been harassing D22 all week. That is all i heard about all night. He has brought up OW3 once again and his current little lady got pissed. A week-end of crap is what my daughters called it.He gets under everybody' s skin but they won' t cut him off. They let it all out with me.
The mistreatment of my children is a huge trigger for me. I stop myself from interfering as they need to figure out how to deal with him. But boy am i angry and fed-up.

If you have no intention of standing, push the D. Get it done. Build a case and push. If you sit on the side line, nothing will get done. Protect yourself. If BPD is it, he will retaliate and will be forced by law to settle this.