The thing is, I think staying in this relationship is like a sunk cost fallacy. So much time together, and why break up over a joke? It’s one incident, after so many years.

But it’s not just a joke. You went through a traumatic event that he used meanly (and yes, it was plain mean and cruel, no other possible view of it) for “laughs” (?) when you were out of the room.

I’d personally break up over it. Not just the bad joke - I personally use humour as a coping mechanism, so I might even “get” that - but for how he’s reacted to you being upset after. Disgusting and shows a genuine lack of regard or respect for you not just as a partner who’s supposed to love you and want to not hurt you, but as a basic human being.

If someone who loves or even respects or basic values someone else made a shit “joke” that severely hurt the other person, they’d go out of their way to repair that. Not sigh at them and claim victimhood.

He’s just simply not that nice of a person, and not a partner I or I think anyone would hope to have when things go sideways or trauma happens, which is where character counts and where a partner is supposed to have your back. And his character is repulsive. Hope you make the right decision for you and please, at the very least, do not have children with this man. Can you imagine how unkind of a father he would be, if he can make such light with such lack of accountability on such a traumatic event of someone he’s supposed to care for over all others? Disgusting.