The differentiation you make between pwBPD being high or low on the spectrum is interesting and it makes sense. This makes me think about the child board. There are a lot of examples of young people that are high on the spectrum. You all should definitely do some reading over there, and if inclined, get involved in the threads. The posters on that board are incredibly strong people. They’re parents of children wBPD.
JNChell this is a great conversation, thanks for the shout out for us parents on the son/daughter board,

it means a lot and for encouraging others to join us, I hope folks do, many share similar struggles in understanding our unique situations and the complexity of BPD.
From my experience the most important factor influencing their ability to have a functional relationship, is the willingness to deal with their problems in a healty way and the ability to self-reflect. And commitment to therapy plays a big part in that.
Purplex I am fortunate to be in the situation you describe. 30DD (quietpwBPD, internal rather than external) diagnosed in 2015 BPD co-morbid (it was a relief to her, answered all her and my questions and opened up the opportunity for the right treatment) so that places her 8/9/10 on this scale. Today after 14 months DBT, getting her meds right, a 12 month break from treatment, presently on 20 week DBT skills group refresh, possibly schema next - I'd optimistically place her at 3. She's using the tools, skills we learn here, she's managing her BPD-she's gradually, in small steps addressed/ing the long list of dysfunctional behaviours, the latest triumph this last year is her eating disorder. I'd add to this, she gave up work Dec 2016 to focus on getting well, she lives at home, the external stress, pressure of life removed for her, if she did not have this support, of family, amazing friends and colleagues and her determination I'm not sure where she'd be now. We've all been totally honest and open with everyone. This year her goal is to get back to work. So that's my share, I hope it helps others.
JNChell, You believe your ex's family, hides, enables as a group …... I'm sorry to hear you've both been up against this, while it may answer some questions you've struggled with.
I would really encourage you both to become students of the tools here. I have used them and they worked - I got one rocky relationship to a very stable place. Its a little like learning to golf or ski, the tools take skill to be effective, but the tools work.
They do work and it's the same encouraging message to parents skill up and practice, they help improve all our relationships.
JNChell have you got the book The Power of Validation off your shelf yet?
WDx