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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