I have spent much of my marriage protecting my kids and in a recent conversation they confided in my that I should have just left and taken them. They don't hate her but there is lots of anger there.
That is a common perception, "I stayed for the kids." However, that didn't provide the children with a solid example of a proactive, protective and example-to-follow parent. An informed perception is that we should good examples for our children. As an example, not simply that we stayed, but that we had strong boundaries for good behavior. Sadly, the boundaries are ours, not the other parent's. We can't make the spouse have boundaries, he or she would have to want them and with acting-out personality disorders such as BPD that's too-often not realistic. So the boundaries have to be yours. As in, If you push or violate ___ boundary then I will ___. Your action may be to leave with the kids (kids, let's go to a store or park, etc) until the spouse calms down, transfer funds being wasted to a separate account where you can ensure the bills get paid, things like that.
In general, when we realize that the other parent is refusing to attend therapy and/or make progress in therapy then that typically translates into the conclusion and acceptance that the relationship is dysfunctional, unhealthy and unlikely to improve unless we decide to Do Something That Helps.
The reality for many here is that dysfunction and unhealthiness can become such a major issue that divorce is the only practical solution. The ex won't respect our authority as the other parent and so we get family court to be The Authority, since its decisions are likely to be, if not optimal, then "less unfair".
Living in a calm and stable home, even if only for part of their lives, will give the children a better example of normalcy for their own future relationships. Staying together would mean that's the only example of home life they would have known — discord, conflict, invalidation, alienation attempts, overall craziness, etc. Over 30 years ago the book Solomon's Children - Exploding the Myths of Divorce had an interesting observation (the earliest quote I could find) on page 195 by one participant, As the saying goes, "I'd rather come from a broken home than live in one." Ponder that. Taking action will enable your lives, or at least a part of your lives going forward, to be spent be in a calm, stable environment — your home, wherever that is — away from the blaming, emotional distortions, pressuring demands and manipulations, unpredictable ever-looming rages and outright chaos. And some of the flying monkeys too.
What if the kids are grown and have their own lives now outside your home? Then your decision is more about you than about minor kids... .though I would think improving your life would, even if a bit late, be an improved example for your kids. With education about PDs and how to deal with them then you can make
more informed and
more confident decisions.
Your children too would do well to consult some counselors or therapists who are experienced in the impact of acting-out PD family members. The past can't be undone or rewritten but it can be recast in a more informed perspective so the future is more positive.
Know I need to leave but for some crazy reason can't seem to pull that lever and go.
It's hard to change after so many years. The first steps are the hardest. Getting a therapist was a major step. Coming here was another, we have an immense storehouse of hard-won experience regarding what usually works and what usually doesn't. Keep on this path and each subsequent step will become less difficult and clearer too.
In time you may wish to share this site with your children but beware that this community is a safe place for those with BPD people in their lives, not for those persons who are acting-out with (BPD, etc) behaviors. Your spouse, their mother, should have her own therapist if she is to make any sort of recovery from BPD.