Good question.
One thing that stood out to me was this:
I’m really struggling not arguing and explaining. He asks pointed questions
I wonder if the questions he asks come across as questions that, if a "broadly normal" person asked, would be answerable (and finished) with an explanation. I.e., the words sound like they could be normal. It's not like he's asking some weird "Do they believe I'm a space alien" question, or jumble of unstrung words. Perhaps the questions are ordered and phrased in a way that "tricks" you into thinking "this is a normal thing a normal person would ask"?
I ask because my sense is that often, pwBPD can use words and language in a way where we think they mean something a normal person would mean -- the literal words match. But, because their minds have a different organization, the connection to meaning of the words is pretty different. Normal-ish words on top, TOTALLY different understanding/goals "below the surface".
So I think you're on to something when you suspect that he's doing
what I can only assume is an attempt to draw me in.
Normal-ish words and questions, often about a 3rd party, but his goal isn't dialogue/discussion, it's getting his emotional (unspoken) needs met.
I wonder what would happen if you put some of the work back on him. Right now, it seems like the work is on you -- YOU have to answer the question, YOU have to engage, YOU have to XYZ.
Couple of ideas to return the work to him:
One is, when he says something like "Why do you thing your mom hates me" or whatever, try:
"Oh my gosh... why do you ask, babe?" and see where that goes. You aren't assuming you understand what he's implying or referencing. He has to do the work to be clear about what's going on.
Another is, when he asks that kind of question, try:
"Wow babe... that's news to me. Lots to process. I'm going to think about that tonight, let me know tomorrow if you want to keep chatting about it over coffee..."
Again, this puts the work on him. You aren't saying you won't talk about it. You're setting some terms for yourself -- you aren't talking about it now, yet you're open to him raising the issue again tomorrow. This puts you more in the drivers seat for what works for you, and requires him to take responsibility for keeping the conversation going, if that's what he truly wants.
A third option could be: "This must be important to you, because it's been brought up before. What new information do you have to share with me about it?" This could be tried if he tends towards repetition/circling/hyperfocus on "an event" or "the incident" over and over and over. Be open to "new information" and decline to participate in rehashing old rumination with him.
Of course, you may have tried these ideas already. You know him better than I do, so you can think about if they'd be effective, if you haven't tried yet.
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Quick thought here:
Is asking him the next morning why he was mad at me and making a (failed) attempt at explaining myself really b****ing? I don’t think so but I’m starting to question it.
In a "broadly normal" relationship this can work -- waiting until things have cooled down to get some understanding. In a BPD relationship, which many here describe as a "high needs" or "special needs" relationship, as you're seeing, this may not be as effective as you would hope.
To stay in a relationship like this, where questions like these come up
is coming upstairs to get my pillow after feeling blown off really worthy of being given the silent treatment?
you may need to develop a "bulletproof" sense of inner self. Typically, you could discuss something like this with a partner, have some back and forth, and move on. In your relationship, you may need to have that dialog with yourself -- to know that no, you didn't do anything crazy. Maybe getting the pillow was a 3 out of 10. It wasn't insane or unprecedented. You're going to have to know YOU, dialogue with YOU, and get affirmation and closure from YOU.
Yes, there may be times when he is in a zone where he can have some insights, be at baseline, and you guys can have some normal dialogue. That's good when it happens, yet it may not be the norm. The question for you is if you can be OK with having a relationship where you may not get the conversations, explanations, and closure together as a couple that you would want. Can you be OK with doing >50% of the emotional heavy lifting? Can you accept his limitations, that he often can't mentally provide resolution or participate in healthy recaps of what happened?
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On the plus side, you're asking about different ways to address the emotional-engagement-seeking, drama-triangle questions. Interesting that both you and Husband2014 report hearing questions that aren't just "babe, how is our relationship doing", but are questions that (a) bring in a close 3rd party, and (b) have emotional traps built in. Circling back, yes, you are probably right that these aren't "face value" questions that can be solved with explanation.
So it's very possible that even in a "high needs" relationship, you can make changes to how you interact that can make things "less worse" and more tolerable for both of you.
Declining to engage with those questions on his terms can, in a way, allow him to figure out how he's going to soothe himself. Right now he perhaps gets some "venting" or "relief" when he can dump on you "See, your mom hates me, I have proof, and you're on her side". When you try different ways to put the work back on him and/or decline to engage, he may then have to find ways to soothe his own inner feelings. This has the potential to be a better path forward for your relationship.
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Lots of food for thought. Hope a few of the suggestions are helpful;
kells76
