Hi LilMe,
Sorry I didn't see this until now. Be gentle with yourself about your choices -- these relationships can emotionally injure us and wear down self esteem. Many feel depressed and that makes it hard to problem solve and see things clearly.
A couple of things have helped me with my own son, who was developing BPD traits like his dad. One was validation, but even more than that, asking validating questions. S14 seemed to have no capacity for solving his own problems. As someone who tends to fix and rescue, I really contributed to this. I found these resources really helpful, especially the validating questions:
And your experience with BPD dad calling the kids liars is a big one. Something I started to do with S14 about 4 years ago is teach him the difference between lying, forgetting, privacy, withholding. Richard Warshak is an author who talks about this in a book called Divorce Poison, mostly because these very tricky situations come in divorced homes when one parent is BPD, where the other parent is accused of lying. I had to really unpack that concept and help S14 see how nuanced it was.
So I would toss out scenarios and we would walk through the exercise together (trying to make it fun). For example, I would give him an example of his friend coming over to play and in the scenario, we have popsicles in the freezer. If friend wants a popsicle, and S14 knows there are popsicles, but says no, is that lying? What if S14 doesn't know there are popsicles? What if S14 forgets there are popsicles? What if S14 knows there are popsicles and also knows his friend is on a strict diet because sugar can make him sick?
I used movies and we would discuss the nuances, sort of like an ongoing lesson, over and over and over. So when he would come home from his dad's and say, "You lied about xyz." I could validate him first, "I would feel really upset if I thought my mom lied about that. How do you feel about that?" And then I could ask him some validating questions along the lines of our conversations about privacy and lying and withholding, etc.
On a separate note, when I lived with my ex husband in the home, I talked about how we would handle some of our most constant points of pain, like blow ups at the table. I think it helped S14 to know that we had a plan. "When dad gets angry at the table, we have some choices. These are the choices I see, and I am going to pick the one I think will minimize conflict. We can regroup after when it feels safe and debrief about what happened."
It didn't always work. My son always wanted to fix his dad and often would blurt things out. I do think it helped him manage his anxiety, and he was definitely relieved to know that he wasn't alone, or the cause of the outbursts.
What might happen if you asked the kids to walk away during a 15-minute screaming fit? My son used to run to his room, and I think it made him feel like he was being a coward. I wish I had been more empathetic with him, maybe reinforce that he made a good choice to take care of himself like that. And to let him know that I also found the screaming to be hard, so he felt less alone about being in distress.