You are absolutely right Anvil... I naively thought that the cause of them being awful for so long was bc I tried to engage regularly. I thought a) AH is gone b) I have no contact with the in laws so I am home free and don't have to worry about them ever contacting me again.
Clearly totally insane/naive on my part. So, MIL's email last week threw me and I have found myself reacting as I always did.
Now it is clear that nothing I do or don't do will stop his family (apparantly for the rest of my life?) from casting blame at me at any old time. I have his family's emails blocked so that's a non issue now. I just got sucked into caring what AH thought and wishing he'd tell his family to lay off and obviously that was really a ridiculous thing to think he'd ever do.
Thanks to everyone for the perspective and experiences and wisdom. I do already feel better. Thank you!