I seem to get no traction on the BPD issue with my legal advisors or social services. I think the BPD should be a significant factor but it is almost as if bringing it up harms my own case
This is unfortunately not uncommon for many of us here. It's a tightrope walk like no other.
The good news is that there are specific communication skills that can help, especially when dealing with third-party professionals.
Amazing turnarounds have happened for dads here who have been dragged through false allegations and custody battles. It's not an easy journey, and it's not all bleak.
This is one of the best places to gather information about how to navigate the legal system when you've been wrongly accused by someone with BPD.
Have you read Splitting by Bill Eddy? That's also a good source of info.
Divorce Poison by Richard Warshak is probably necessary for your situation too.