after you divorce does the spouse turn on the kids or can they throttle back.
My experience is that divorce can shine quite a bit of light on malignant behaviors and a BPD spouse can throttle back in some ways but ramp it up in others.
Professionals get involved and scrutiny of bad behaviors often increases. Even the perception of scrutiny can cause things to change.
Anecdotally, it does seem that fathers with BPD are more interested in *winning* than in parenting. My ex fought for more visitation even when he wasn't able to make good on what he already had. He wanted control over decision-making without doing any of the work, similar to how he had been in the marriage. Every issue that required some kind of cooperation turned into a bizarre, irrational long-drawn out battle.
The dark downside is that in his attempts to become the greatest disney dad of all time, he begins to practice parental alienation. If you aren't seeing signs of that already, it's a good idea to read up on it so you can counteract things. Alienation is very insidious and psychologically mind bending when it involves kids who aren't as developmentally able to understand what's being done to them.
A good place to start is Don't Alienate the Kids by William Eddy and Divorce Poison by Richard Warshak. And anything by Dr. Craig Childress who you can find online. He's a bit academic at times but has great tips.
How do the kids get along with their dad right now?
What is their relationship like with him?