Hello Akindman and welcome to the group

BPD relationships can be difficult and unintuitive, with lots of hurt. I hear what you've gone through, and it's a lot. Good to know you have a therapist for yourself right now -- great move. Also good to hear that your W is in therapy.
I may have missed it; does your wife have an official diagnosis of BPD? If not, when or how did you begin to suspect it might be in play?
I just want her to get better and learn how to be a better partner. I want her to develop a stronger sense of self and not to hurt as much. She is going to a therapist again and seems to be committed to continuing therapy. I have hope that I can keep myself safe and strong and support her recovery. But dang I sure need help doing it. I have never loved or been so deeply loved. Some of you may be thinking this sounds sick and maybe it is but I have faith we can get better. Our backstory is Ling and complicated and I have plenty of regrets of my own that I have not mentioned here. But to be clear I have always been faithful to her and always will. I see hope for us because we have made it this far and it has been just as bad or worse in the past. I know we can grow together and become better versions of ourselves. Saving my marriage is what I want more than anything in this world.
One of the unintuitive things about BPD relationships is that both parties can have, in different ways, a weak sense of self, that can contribute to the relational dynamic. What I mean by that is we often think it's "selfish" or "self-centered" to focus on
who we are as individuals, in these relationships. "I should be helping her!", or "she needs my support", or "if I did more for her, she'd know I loved her", or "I need to sacrifice right now for her recovery", etc. Those mindsets keep the spotlight on the pwBPD: what does she want, what does she need, what is she going to do, what is she thinking, how is she feeling.
That kind of lopsided tilt in focus isn't good for the relationship. It also hinders the non-BPD partner from the growth needed to be healthy in that high-needs relationship. As counter-intuitive as it sounds, it can be better for the relationship for the non-BPD partner to start focusing... on themselves. Therapy is a good first step. Shining the spotlight on who you are, what your past is, what you want, what you like to do, what you need to take care of yourself... those are all critical if the relationship is going to have a shot. I wonder if anything in our workshop on
What does it mean to take care of yourself? stands out to you?
Right now I need help knowing how to respond to her BPD rage moments. I know to walk away and take a walk to cool off. But I need to know what words to say to set boundaries when she is being verbally and emotionally abusive, so that I don't participate in the fighting and perpetuate the cycle.
Boundaries are an interesting, and also sometimes unintuitive, concept.
Boundaries are rules we have for ourselves, that are 100% under our own control, about what we'll choose to let into our lives.
It's good to hear that you're open to learning more about boundaries, and that you recognize that boundaries -- which are for your own protection -- can be needed in high-conflict situations.
You're already setting a boundary, actually, by choosing to walk away and take a break when she rages

Tell me more about the desire to have words to go with that. Would the words be: for your own sake, to try to explain it to her, to add on to the action, because you think you have to say something for it to be a boundary... some other reason...?
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Also, have your therapist and her therapist been released to talk with each other?
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Fill us in, whenever you get a chance. We're glad you found us.