Self regulation when partner knows how to press my buttons and encouraging help

[Northern17]

I’ve been with my wife for years. She has never been diagnosed with BPD, so I don’t want to diagnose her myself, but after years of trying to understand our relationship, a lot of the patterns seem consistent with BPD traits.
She is very high functioning in most areas of life. The problems are overwhelmingly in close relationships and become much worse under stress. We have had long periods where our relationship was genuinely good, particularly when life was less stressful. When stress increases, though, things can deteriorate dramatically.
Some of the patterns I see are intense reactions to relatively minor perceived slights, interpreting ordinary mistakes or disagreements as evidence that I don’t care/listen/respect her, difficulty accepting my perspective once she feels hurt, anger that seems disproportionate to what happened, and what feels like punishment or retaliation after she believes I have wronged her.
The retaliation is probably the hardest part for me. She sometimes acknowledges that she is deliberately doing something because she knows it will upset me. She might withdraw, slam a door, abruptly leave a conversation, swear at me, or continue pushing an issue after it is obvious that I am overwhelmed. It can feel like once she believes I have hurt her, hurting me back becomes justified.
Over the years she has also learned exactly what affects me most. I have become extremely reactive to some of these behaviors. Sometimes an incident that objectively isn't enormous sends me into a massive emotional and physiological reaction because it feels like the thousandth repetition of the same pattern.
We recently had a baby, and the additional stress has made things substantially worse again. One example: while I am soothing the baby, my wife will sometimes hover and give unsolicited instructions. If I cannot hear her over the white noise or don't respond correctly, it can become another conflict. I have noticed that I now sometimes become angry or anxious when the baby starts crying—not because I am angry at the baby, but because I am anticipating my wife intervening and another conflict beginning. I really hate that this dynamic is contaminating something as important to me as caring for my daughter.
I'm starting individual therapy because I need to learn to regulate myself better. I don't want my wife's behavior to have this much control over my emotional state. I want to be able to recognize when I'm being triggered, disengage, and recover without eventually boiling over after enough button-pushing.
My two main questions for people who have lived through something similar:
How did you learn to regulate yourself when your partner knew your vulnerabilities extremely well and continued pushing after you were already overwhelmed? What actually worked beyond generic advice like breathing exercises or “don't engage”?
Is there realistically anything you can do to help an undiagnosed, high-functioning partner recognize that they need professional help? I'm afraid even suggesting couples therapy will immediately become evidence that I think she is the problem, and suggesting that she individually needs help seems even less likely to go well.
I don't expect to change her myself. I'm trying to understand what I can actually control, what boundaries work when the other person doesn't necessarily respect them, and how to judge whether meaningful change is realistically possible.

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PLEASE - NO RUN MESSAGES This is a high level discussion board for solving ongoing, day-to-day relationship conflicts. Members may appear frustrated but they are here for constructive solutions to problems. This is not a place for relationship "stay" or "leave" discussions. Please read the specific guidelines for this group.

[Pook075]

Hello and welcome to the family.  I am so sorry you're going through this and it does have a lot of similarities with BPD.  While we're not here to diagnose, that really doesn't help or hurt anything because the path forward is ultimately learning to communicate in a different way so it resolves conflict.

How did you learn to regulate yourself when your partner knew your vulnerabilities extremely well and continued pushing after you were already overwhelmed? What actually worked beyond generic advice like breathing exercises or “don't engage”?

Hopefully you realize that this is a "you question" and not a "her question."  It's a great question to ask and it's an opportunity for you to grow as a person.  The answer, however, comes down to you handling conflict in a healthier way.

For instance, you mentioned that you're already overwhelmed.  From what?  Work, finances, a new baby...did I miss anything?  What can you do about each of those things to let go of some of that stress?  If it's money, then there's two potential answers- get a better job or budget your finances better.  If it's home life, then find a better balance that works for you.

It's common for those close to BPDs to also have mental health problems from the abundance of stress and the levels of conflict.  It leads to depression, anxiety, sleep problems, etc.  While you can't "control" your wife, you can control how you react to her and the bigger issues I just listed.  Eat better, get a healthy sleep routine, get in therapy to learn to let go of negative emotions and stress.  Get in the gym to work on getting healthy, which naturally boosts your mood and the ability to deal with the stuff at home.

What actually worked in my life was taking control of my life.  The buttons that my BPD ex and BPD daughter pushed, I learned to let go of that stuff and avoid the conflicts entirely.  I accepted that they were sick and I wasn't in control of that.  But I was in complete control over how I reacted and what I let get to me.

Is there realistically anything you can do to help an undiagnosed, high-functioning partner recognize that they need professional help? I'm afraid even suggesting couples therapy will immediately become evidence that I think she is the problem, and suggesting that she individually needs help seems even less likely to go well.

Let's flip this around.  I just gave you some pretty hard advice to swallow.  Honestly, how did you take it?  For most people, it doesn't go over well when you tell them that part of the problem is within them.  They get defensive or angry.  They push the blame right back to the other person.  So however you reacted to my advice, your wife will likely react 10x worse.

I said this earlier, but I'll say it again more directly.  Your wise is not "the problem".  How the two of you communicate and how you handle her mental illness is the actual problem.  You can't "fix" her and neither can a therapist or another professional.  Suggesting it is blaming her, and she does not react well to blame because she's mentally ill.

What you can do is meet her where she's at, show compassion for her struggles, and learn to avoid the worst of the conflict by communicating in a different way.  It is incredibly hard at first and it's not intuitive, but it ultimately solves both of your questions because it relies on you to make the necessary changes.  And that's good news because you control you.

I hope that helps and again, welcome to the family!