Has anyone else dealt with something like this, where your coping behavior ended up being wrong as well?
Yes. In my case, the constant barrage of criticism, undermining and rage over a period of ten years meant that I convinced myself that I was a really bad person, responsible for 100% of the problems in the marriage. Out of desperation, I then did something illegal, which led me into therapy for the first time, where I finally got some clarity.
I don't blame myself for what I did, because I really didn't understand what was going on, and I was doing the very best I could with the knowledge and skills that I had at the time. Things are very different now, and I would not do the same thing again. I have also paid a heavy personal price for my actions and continue to do so.
People wBPD can be very charming, convincing and charismatic and it is not unusual for therapists to be misled by them. Have you had any joint sessions with your wife's therapist? I have found occasional joint sessions are good for giving therapists a reality check, and seeing that we are not the ogres our BPD partners make us out to be.
Otherwise, as Notwendy says, the best thing you can do is to continue to work on your own therapeutic journey.