Dear madmac27,
This website may be helpful to you:
www.highconflictinstitute.com. Divorce and child custody cases involving one or both parties with mental health conditions, including BPD, are sometimes called "high conflict cases," and there is a wealth of information about them on this website and others. The High Conflict Institute was founded by Bill Eddy, an attorney, mediator, and licensed clinical social worker, who is considered one of the leading experts in managing these cases.
As Eddy has stated in a number of articles I've read, spouses with BPD can be very successful in charming attorneys, judges, and others, and in persuading the court that THEY are the sane party, and their NON-BPD spouse is the "crazy," abusive, and/or unfit one. Given what we as former partners know, this is a very believable assessment of the situation. He recommends finding a lawyer that is up to speed on BPD. There are, apparently, a number of lawyers and law firms that specialize in these cases, and are better prepared to protect the interests of the non-BPD spouse and their children.
I hope that helps!