From what my T has told me (and what I've seen from my uBPDm), someone with BPD can switch up who's "all-good" and who's "all-bad". It sounds like your mother has done that in the last year, and that's probably why she's bombarding you with calls and texts. She wants validation, and she has chosen you to give it to her.
Do I want to go there to be a whipping post and hear nasty comments about my brother?... . no, the answer is no. so shouldnt it be so simple? then dont go over there. Im not going to, but it still isnt easy and causes me worry for the future. I just try to keep telling myself the angst that she causes me is not worth it, and I need to take care of myself.
You do need to take care of yourself and your children--that's the most important thing. You are taking steps to improve your life, which is great. Is there some middle ground, where you can involve your parents and not be subject to calls and texts 24/7? What kinds of boundaries can you use to protect yourself?
It hurts me deeply that my father enables her behavior and does not stand up for his children, but what can I do? As they sit alone at their house and their children and grandchildren are not around- will they realize its them and not us?
Unfortunately, since your mother disagrees with her diagnosis, it's unlikely that she will realize that she's contributing to what's going on. You're right--the best way to get through this is not to hold out hope that she'll change, but to work on yourself and develop healthy ways to deal with her behavior.