Hi Jabberwocky;
Glad you both made it to couples therapy. It's a good start.
This comment stood out to me:
Interestingly the couples therapy was all focused on me. I did tip the therapist off that I thought that she was struggling with BPD traits, but the most significant amount of time was spent encouraging me to keep exercising.
My take is that there's a reason for that, and it may actually indicate that the therapist "has her number" so to speak.
Sometimes when multiple parties are starting therapy, it can be the case that one party is more invested in doing it and wants it more than the other partner. And/or, one partner may be more sensitive to criticism and more reactive than the other.
What a good therapist needs to do is to build trust and "buy in", not just from one party who already wants to be there, but from the "lowest common denominator".
Basically, the T has to create an environment where the lower trust party buys into the process. If there's even a hint that "the non and the counselor are ganging up on the problem pwBPD", then the pwPD, understandably in a way, probably won't come back.
If the point of couples counseling is to keep both parties "in the room", the T has to start not by hitting "the issue" head on, but by building trust.
So, the T models "hey, this isn't going to be a black-and-white, good guy-bad guy scenario... see, I'm working with the NON person, the NON person has a lot to work on too". This probably won't be described in words, but acted out in how the counselor is focusing on you first, trying to work with you, and doing it in front of your uBPDw.
This builds trust in the process in your W, who may feel less blamed/ganged up on if she's like "well, the C is telling Jabberwocky to do stuff, so I guess the C isn't taking sides".
Nutshell version, this sounds to me like a really, really normal start to couples counseling (or other multiparty counseling) when one participant has PD traits. If you know that, it can make it easier to "go with" the process as it starts. The next few sessions may continue like the first -- a lot of focus on you and "your issues". If you can understand that that's a strategic decision I hope it makes it easier.
Don't let that mean you don't genuinely do the work, though! It's not that the counselor is like "well Jabberwocky has no issues, so I'd better make up some stuff for him to work on, to be fair"

of course, I know you're not thinking that.
Truly engage with the HW the counselor gives you, and know that the sessions are starting like this for a meaningful reason.
Best hopes that your W buys in to the therapy and engages in a genuine way.
Keep us posted on any updates;
kells76