Hi ChiRunner and

You're not alone in coming to the realization that BPD could be involved, long into your marriage. "Awakening to a full realization" makes sense, yet the question remains for you -- you can't "fall back asleep" but what do you
do?
A lot will depend on the variables that are unique to your situation. While there are
general skills for improving a relationship when BPD is involved (and, the great thing is that even if it isn't BPD, learning and using these tools and skills won't make things worse!), each pwBPD (person with BPD) is unique, and family structures are unique as well. Your W may have no chance of changing, or she may -- BPD is not a "death sentence" though it is challenging for couples to cope with, especially if untreated. Learning more about your situation will help us support you better.
How old are your kids? How have they been doing with home life?
Have you and your W ever done couples/marriage counseling?
Do your individual therapists have releases to talk with each other?
Has there been any physical violence?
...
Right now we're on the "Bettering a Relationship" board, where the focus is on what's under our control to change in the relationship. While the dysfunctional dynamic may not have an exactly equal 50/50 split (i.e. we're not saying "you both are equally at fault"), by definition both parties contribute -- somehow -- to the current relational dynamic. Fortunately, it is totally possible to change your contribution to the dynamic, without needing your W to agree, understand your point, feel happy about it, or cooperate.
No matter what you decide, the tools and skills we work on here on Bettering are valuable -- after all, even if a marriage ends, the two of you remain coparents, and relating more skillfully and with less conflict will benefit your children. Do know that the focus on Bettering is on learning and using the tools and skills in your marriage, not on making suggestions about leaving (just FYI). You are welcome to also post on the Conflicted/Divorce board if you feel stuck, aren't sure you want to try the tools/skills, and/or need legal advice.
...
Couple of thoughts about your situation specifically:
After her latest barrage of cruelty and anger, I and have told my partner that I want emotional space to work with my therapist (8years in therapy) to work on stating my position and moving toward next steps. I have for years known that I would have left this relationship a long time ago were it not for the kids. But I now also understand that I was not ready to leave the relationship because the emotional abuse has destroyed my sense of self and my self esteem. However, the full picture of our dysfunctional relationship is becoming much clearer to me through the lens of BPD and understanding of emotional abuse and its effects on my ability to think for myself and honor my needs as a sovereign person.
What did that look like to tell your partner you wanted emotional space to work with your therapist? What was your goal? How did your W respond?
One of the key mindset shifts that can improve a relationship when BPD is involved is that we don't have to "ask permission" to take care of our own needs, and we don't need to announce to our partner that we want them to do something that's actually under our control.
pwBPD seem to be impaired in their ability to manage their emotions. Their emotions can be harmfully intense and can vary wildly, to such a degree that they are totally wrapped up in their own emotional turmoil. Wanting a BPD partner's agreement to "give emotional space" when they can't even regulate their own emotions, may be a dead end -- could be more fruitful to focus on
our own boundaries (not ultimatums!) and values.
I may be missing the "feel" or "vibe" of that interaction, so fill me in and let me know if I'm off base.
During this break from my wife, I have remained calm, assertive and civil and not let her know that I have come to these conclusions about her mental health. Ironically, my wife who has been in therapy for 20+ years just old meant she plans to stop therapy because she doesn’t feel it can ball her anymore. It has long been suspicion that she is gaming her therapist into supporting her POV. And I now suspect that perhaps her therapist has started to address things that might bring her BPD traits into the light, so my partner decides she needs to stop seeking help. My therapist and several resources advise me not to diagnose my partner, but instead focus on defining by personal boundaries, doing a lot of journaling and beginning the work of healing so that’s what I’ve been up to. After just over a week of establishing space from my partner, I already feel some of my vitality and confidence returning. I cannot go back to the way it was before.
In terms of what's going on in someone else's therapy... I mean, maybe she is "snowing" her T, maybe she isn't, because after all, I'm guessing that anything you hear about how her sessions go is from her directly? My suggestion would be that unless you hear it
directly from the therapist, take it with a huge grain of salt. BPD can impact perceptions, memories, and feelings, so even if she were working on "the right stuff" in therapy, it may get filtered back to you as "my therapist agrees with me that you're the source of all the problems, and I'm doing great and can graduate from therapy". Don't spend valuable mental time on that. She's an adult, and it's up to her how she manages her mental health care. You may wish or want for her to stay in evidence-based therapy, but it isn't something you can make her do. You can decide for yourself if you have a
boundary (a rule for yourself, not a rule for anyone else) that you are able to stay in relationships with people who stay in therapy, but that isn't making her do anything, it's being clear with yourself what you are OK with.
I'll also comment that it's OK to give yourself some time to adjust. There are a lot of changes in the dynamic happening, and you mention that a week has gone by. You two have been married for 14 years... you didn't get here overnight, so consider letting things play out a bit more before feeling like "this is how it's going to be". Change is hard -- I'm in therapy right now and even though intellectually I understand that I can make hurtful relational choices, emotionally it remains difficult to change them.
It also seems incredibly clear to me now that there is no chance of my partner changing and certainly no chance of making this marriage into one that I feel happy in. Yet I am having second thoughts about ending it outright. I sense that my hesitation is based on a flimsy wish for my partner to one of those who are able to combat the disorder and make it out. That it would be worth it to save my kids from the torment of watching their parents dissolve a marriage and instead try to heal a broken home.
You changing your contribution to the dynamic, will change the relational dynamic. There are no guarantees that your W will change -- but she may, in response to your changes (like if one dance partner stops doing the "expected" steps and does new steps). Note that that isn't the same as "if you just pull this level then it's guaranteed she'll do XYZ". You can take steps to make your life more livable for you -- she may join you, she may not, but either way,
your life becomes more livable.
It won't be easy to work on improving the relationship. Again, by definition, BPD impairs a person's ability to regulate emotions and to have "generally normal" intimacy. That means she may not "do her fair share" of "the work", just like a person in a wheelchair won't do "their fair share" of "climbing the ladder". Knowing ahead of time that the lion's share of personal work will fall to you, may help you avoid the dead end of resentment and find more effective ways forward.
What has your therapist thought about your hopes for your kids?
Not sure what to do, how to proceed. But I feel like I have to decide soon.
Where do you think that feeling is coming from? As you step back and examine that feeling, do you think it's true? Not true? Other?
Thanks for hearing me out. I appreciate that this forum exists and that there might be someone who can understand what I’m going through.
We do get how difficult and unintuitive these relationships can be. While neither my H nor I have BPD, his kids' mom has many traits/behaviors, and I've been a member here for ~9 years to get support in how to cope more effectively. Standard "stepmom" advice does not cut it -- and I'm so grateful to have learned so many tools and skills here; it's improved our family life dramatically.