I agree with FD -- understanding BPD is not by itself what you need -- and unfortunately BPD is not something lawyers learn in law school (although wow, wouldn't that be great?). I don't think they need to know what BPD is in order to be an effective lawyer in a high conflict case. It helps, but it isn't essential.
What makes a really good lawyer is a really good client. To become a good client, you have to understand as much as possible about the disorder, about yourself, and about what you want your lawyer to do (no continuances, no back room deals, etc.). The last part takes some experience, which is what this board can offer. But just as helpful is Splitting: Divorcing a BPD/NPD Spouse by Bill Eddy.
This article is also really helpful -- it's written by lawyers for lawyers, but it spells out the type of approach that is effective in high conflict cases. It gives you a small peek into what they have to keep in mind when they find themselves involved in a high conflict case. You can give the book or article to your lawyer, or you can guide your lawyer accordingly.
There have been over 60 filings in my case in a 4 year span. That's averaging more than one filing a month for four years, which is extreme by any measure. I didn't read this article until recently, but it is exactly what I would recommend to someone dealing with BPD and family court.
The lawyer you have who recommends trying to get what you need outside the court doesn't understand what he's dealing with. You are being a good client when you push back -- your lawyer works for you. A lot of lawyers don't propose strategies, but it goes a long way because these cases tend to be more like chess games than one-time events where everything gets solved and people cooperate.
There are tools you can use to develop a good strategy. One is to find a skilled mediator who is accustomed to dealing with narcissists, especially if your ex has a lot of entitlement. The other is to use a deposition -- this flushes out BPD lies that can then be used to undermine her credibility in court. Another is to get a custody evaluation or other third-party professional involved who will provide so-called "objective" testimony in court. All of these are expensive, and all have pros/cons. The key is to understand how the system works where you live. And make sure you stay on top of your lawyer. For example, I learned that it's important to have my lawyer write all of the orders. I always made sure she included consequences where applicable, like "failure to comply by the deadline will result in sanctions for legal fees." Court does not enforce court orders, that job falls to you. So if you know you're going to end up back in court, you want to make sure the consequence that YOU want is in the order so that the judge doesn't let the other party take a second bite of the apple.
No matter what strategy you use, document everything. It's critical. Otherwise it turns into he said/she said, and court is useless if it comes down to that.
It's hard to find a good family law attorney who knows about international law. I had to do all of that research myself (I'm canadian, living in the US, my child is a dual citizen) and explain to the parenting coordinator, my lawyer, and the judge how the Hague Treaty works and what others have done in my situation.
Being an assertive, reasonable problem solver who documents everything, who has a strategy and a clear goal, will go a long way. It's more important than whether your lawyer understands BPD, although certainly that won't hurt.