There is a really good book which I think you would find interesting OP.
Stalking the Soul
The author describes abusive families, and how the victim can end up looking as though they are the 'mad one' or 'overreacting'.
Of course you are not 'overreacting' , whatever that means. These people often look like saints to the outside.
The end of my marriage came when my MIL shouted at me that it was my own fault that my father had abused me as a child, and that she thought he was a perfectly nice man, and did I ever think that it was me that was the one in the wrong? This was in my own kitchen, a couple of months after I had had a baby, and I had been married a couple of years to her son.
She came back later to say some more in the same vein. Her son, my H, and my FIL stuck up for her, and I was made out to be the bonkers one. I stayed with her son for another 20 years, until I finally saw the light.
Now she herself was an abuser, as was her son.
The point I am trying to make, is that her son, my H, chose to see the public face of my parents, while they also only showed their own 'nice side' , and in doing this they blamed me, their victim, for what was happening to me and what had happened to me.
Victim blaming is everywhere. It's the easy way out for people who, for whatever reason of their own, deny the actual truth of the situation.
I am not explaining this very well, but from my own perspective now, four years on from leaving that family, I can say that my reaction to your H's attitude is that if he wants to send a card let him do it from his own new home, where he is living without you!
If I am being generous to your H I would say that he has not had any experience of abuse, and so , to him, it's just a bit of a family fallout and if everyone just puts it behind them everything will be ok again.
With my other hat on, however, I would say that he is as manipulative as your mother and S-Father, and is not a very nice person.
Only you know which is the actuality.
People who have been abused often choose partners who repeat the abusive pattern of their own parents. They mistake abuse for love, as that is all they have known. I did this.
Have you done this? Or is your H just not understanding the situation?