Yeah, child comes first. It sounds like your husband also understands that.

But, you come second. I hope your husband will be supportive of you and will not tolerate the crap your MIL is doing and saying. Which does mean, unfortunately, that he should cut ties with them instead of excluding you from family things. So hopefully he doesn't do that.

I'm really sorry that you've got such a s*** MIL. The ball is in her court to try to fix things with your family, not yours or your husband's. She is the one who acted massively out of line.