Hi emergent,
Welcome to the Coparenting board! I respect how much you are working through this based on your values, about what you feel is fair, and moral. It's good that you're coming to terms with the choice to stay or leave with senior members and peers on the Undecided board. It's a hard choice.
We do have a conversation on bpdfamily that might help you:
PERSPECTIVES: Is it better for the kids if I stay or leave?There have been studies that show that kids who grow up in divorced homes have more problems in life than kids whose parents stay together. Would having a BPD/NPD parent (or other abusive parent) change this outlook? If you leave, do you think your kids have been harmed by the friction between you and the ex? Would things be better for your kids living in a two-parent home situation? If you are the father, do you believe that leaving your marriage means leaving your kids? Other members on this board, and on Family Law, have talked about the benefits of reading The Borderline Mother by Christina Lawson. This is a well-researched book, a bit on the academic side, but very dense with clinically supported information about the effects of having a BPD mother (assuming untreated).
You mention that your BPDw is very devoted and misguided as a parent. This could be putting it lightly depending on your own tolerance for conflict. Many non-disordered spouses grew up in homes where a family member was BPD, or a similar type of invalidating environment. It is easy to accept abusive behavior if we have not come to terms with what healthy looks like, and we then pass this legacy on to our kids.
Every person with BPD is different. Some are outwardly acting, some are inwardly acting. Some are diagnosed and in and out of treatment, others are convinced we are the crazy pots and will not set foot in a therapists office. There are sub-types (waif, hermit, witch, queen). And I think a lot depends on our own skill level managing the abuse. Some people are skilled at this, while others don't have the inclination.
Our own kids and their emotional resilience matters too. My son seems to have the genetic predisposition that makes him highly sensitive like his dad. He was imploding. I left the marriage because he was talking about not wanting to live at age 9 and my ex's reaction would surely make things worse. Not to mention the abuse I was no longer able to manage.
I will say one thing about having children and being entangled with the legal system. It is the 8th circle of hell. I'm in the US, and don't know the laws in France. But it's hard to imagine any system is helpful if it does not have a sophisticated understanding of mental illness.
Trying to get my son the mental health services he needed through the court system was the most soul crushing experience I have been through. The cost, the slow pace, the triggering effect of the court system on my ex, the helplessness.
Any advice I could offer comes through that lens. It is this way for many members here. If you are seeing signs of emotional distress in your kids, take into account that you will not be able to swiftly solve their problems like a normal parent. Again, this depends on whether your wife is high or low functioning, and how her traits are expressed. But if she is like many BPD parents discussed on this board, you will find yourself rendered helpless by the legal system.
I could not allow my ex to stop my son from getting the services he needed -- it would be like letting my son walk off a cliff. Because of the way the legal system works, the only options were black or white, just like BPD. Either he was in my son's life and wreaking havoc, or out completely. And because of the way the system works, if I offer access, then he can go back to court and show that I must trust him. We are fully triangulated by the court system. :'(
You are wise to think this through carefully.