What does your daughter say, about telling him or her grandparents?
My mom had supported my marriage, because a couple of reasons. He entered life during her period of mourning and becoming a new widow. I seemed so happy, he was attentive to her, as a future mother in law, and had been a bit of a mommas boy, before she[his mom] collapsed from a brain aneurysm, several years before me. The family though large, remained(s) a closeknit Italian family. It was hard to judge, he would get vile as time went on. There was dramatic moments, in the beginning, for sure. I didn't provoke what transpired a few years into marriage. I find it, tough, to hear your T saying because of the new dxs of your stbxh, that it isn't abuse if there's no intention? That implies mindreading. Perhaps, it's to help move past into survivor? Certain behaviors are just that.
I know some of your going into marriage history, from other posts. You did what you could and back then, it's just how it was. My mom married my father in '73. She'd said, it's what you did, back then. In school or out. She supported my divorce. My gram and I have had numerous discussions about marriage through the years. Her views, how divorces happen, etc. She paid my retainer.
Not sure if I'd consider marriage again. It's such a rocky endeavor. Perhaps I'm jaded?

Maybe you'll begin the new year, a new woman? Can hope [emoji41]