Dad wants us to "talk"

My dad definitely has some narcissistic traits. Last night he got me to my wit's end.

My mom, also a possible narcissist, and younger sister (YS) got into a fight a few months ago leading to YS moving out and going NC with her. My dad is an enabler and won't recognize that what my mom did was wrong (won't get into it, just the usual tons of no validation as the final straw for YS).

From then on, my dad hasn't had the emotional capacity to deal with it, often wanting us to solve his discomfort. He once talked to the two of us over dinner and we thought we had been okay, but all of his "yeah I know"s and "your mother really is like that" turned out to be just empty, fake empathy/sympathy. He would still blow up and be frustrated about why YS was still not talking to our mother, even though our mom wasn't even reaching out to her. It led to YS also going NC with him, which of course frustrated him even more.

Last night he messaged me that he wanted to talk and get it over with "once and for all". I made a boundary telling him to go to therapy first, to figure out his own issues (he has a lot of temper issues) outside of the family setting - he had told me he had gone to therapy for families but they just told him to talk and talk. I'm pretty sure he didn't show them the walls of text of me and YS patiently enumerating how we felt, and his responses of "you and YS are just accusing me of things we didn't do!!!" instead of actually reflecting on any of it.

Of course, he started throwing a tantrum on text with the full capslocks and exclamation points, all while saying he wasn't actually throwing a tantrum. It was exhausting but he had no awareness about it whatsoever.

In the end he said "You and YS will NEVER EVER make me go to a therapist. You are just saying it's useless to talk to you anymore, so I guess that means we will cut off all communication." Then fine. If his pride over not going to therapy trumps our relationship, then so be it.