I'm sorry to hear you had a nuclear war over the wedding
I'm about to engage with my parents after a lengthy break, and think about this question all the time. I'm working with my T to figure out how to prepare, what to expect, etc. and have been reading a book about dealing with an emotionally immature parent that has been helpful, particularly in terms of my own vulnerabilities and expectations.
Some of the things that I plan to put in place in order to minimize my own stress:
+visiting for only a short period of time, like dinner
+engaging with them as if I'm observing people from another culture (almost professionally polite)
+lowering my expectations, giving up on a "healing fantasy" that they can be different than who they are
+not allowing myself to be seduced or bamboozled by hints of emotional closeness (always followed by a fight)
+if other family members are present, explaining to them in advance what my limits are, if necessary
+not agreeing to any further plans without "checking with my calendar first"
+having ready responses for predictable flare-ups
My T actually encouraged me to audio record my interactions with my parents, which I find strangely calming, just the idea of it! It makes me feel like I'm doing research

and helps me depersonalize things a bit.
I have a very tricky codependent mother who uses emotionality in a slick way to triangulate the family in a way where I end up back in what the book I'm reading calls a "self-role" that the family expects of me, which also happens to be the crappiest role in the family!
I interpret much of this as "arrive late, leave early" and avoid any topic that is remotely emotionally contagious.
In your family, is it the MIL who is BPD? It's possible that physical closeness with your H triggers her dependency and clinging (what Masterson calls rewarding behavior). If so, you may want to agree for that brief time to experiment and see if that is indeed happening.
My SO has a BPD D19 and I notice that when he is physically affectionate with me, she regresses, which triggers dependency and clinging followed by defensive behaviors. As much as I would love the freedom to touch lovingly when we are out together, I find the clinging so difficult to abide that it's a tradeoff I'm willing to make.
I do think mastery is possible in these relationships, and that takes a lot of planning and practice.