Hi again Fulbright87, you're getting some good support from yellowbutterfly. It's such a gift to have this group to come to and to have others say "I get it... I REALLY get it."
...what can I do in these situations? What can be done to avoid them in the first place? How can I safely establish a boundary without activating the immediate thought that I am abandoning her when trying to exit a cyclical argument? How can I exit the cycle in the first place? Is there anything that can be said to calm my partner down, then address the pain she inflicts at a later time? ...
Important questions to ask. It's great that you are open to trying different approaches that are 100% under your control.
A couple of points in your situation did actually stand out to me as opportunities to try something different:
My partner tells me consistently how I ruin their life through stupidity. This is justified by calling my actions stupid (while still using always statements). For example this evening they were complaining about a scent due to sensory issues. I offered to use a room spray as a means to help and did so near our window unit so that it would spread throughout the room with a single application. This opens the floodgates on a rage of how unhelpful I am, questions of how my brain works and that I am a life ruiner. I am then reminded that I cannot be trusted to do anything because I always find a way to screw it up in a way that hurts her even when I am “being nice.” The follow up is that in the midst of all of this I start to show signs of being displeased at being called stupid in any capacity. This in turn is taken as an invitation to call me indignant and disrespectful.
pwBPD process information, emotions, problems, etc, very differently from people without BPD. That means that "typical" approaches to problem-solving, listening, dialogue, conflict, etc, that would mostly work with a "mostly normal" person, generally either aren't effective with a pwBPD, or escalate the situation.
That's a key moment up there -- what happened right after your partner complained about something.
Was it pretty reflexive for you to try to fix it?
There's another option on the table at that pivot point, besides you taking responsibility to fix it. It could look like true validation (i.e. not validating what isn't valid, but finding something in your partner's experience where you can genuinely say "yes, that is how it is"): "Babe, those sensory issues really impact so much of your day... that sucks."
It might be worth considering not fixing things for your partner, but allowing your partner the opportunity to manage and be responsible instead. This may be uncomfortable for you.
Another key moment that stood out to me was this:
The follow up is that in the midst of all of this I start to show signs of being displeased at being called stupid in any capacity. This in turn is taken as an invitation to call me indignant and disrespectful.
I respond by saying that while she has the right to be upset at the actions, that doesn’t extend into insulting and belittling me just because she’s feeling that way. That doesn’t go over well and soon I am being told that old parts of me must be manifesting to hurt her all the time to gain some sick satisfaction at the suffering she experiences. That she’s scared of asking for anything because of how incompetent I am (which I find myself bitterly amused about due to the fact that I take care of all household chores and work related aspects due to her handicaps). Then when trying to reiterate that I am tired and will not engage with a conversation that involves insults rather than addressing and solving problems she tells me that I have degraded her soul to this point, that I have diminished her connection with herself and that again, I deserve things that I would not dare utter back to her.
Learning about true boundaries was a journey for me. The pwBPD in my life is my husband's kids' mom (her H has many NPD traits, so it's... a lot), and early on, we thought that if we just explained to them
enough how their actions were hurting the kids -- if we could just get them to agree to some limits on their behaviors -- then everything would go better. Oh, how wrong we were! But at the time, it seemed so normal -- "let's just all agree together that they shouldn't be doing XYZ, because it's bad for the kids". In a "mostly normal" situation, that might've had some effect. Not when PD's are involved, though.
We need to recalibrate our understanding of boundaries. Boundaries aren't us telling the other person what isn't okay for them to do.
Boundaries are 100% under our control. Have we made a statement, request, demand, etc, that we don't have 100% control over? Then it isn't a true boundary.
Sometimes the difference can be subtle. It sounds so close to a boundary to tell someone "While you have every right to feel ABC, you don't get to take it out on me".
But do we have control over that?
Try this on for size instead:
"I understand you're upset right now. I am able to stay and talk when there's no insults between us. If I hear insults in a conversation, I will take a break elsewhere."
or
"I can stick around to talk when there's no belittling going on."
The followup would be acting out your boundary by staying to talk when there aren't insults or belittling, and having the strength to leave the room when she starts.
Notice that key difference -- it's not about how she can't or shouldn't insult or belittle you, as you can't control that. It is about what you will or won't accept in your life. You make statements about what you're up for, and you follow through when things happen in a conversation that you've decided aren't okay with you.
...
What do you think?