The one thing that struck me about your post is that you and your Mother-in-law emailed each other. I think this invites problems rather than solving anything. Stop all messaging and only interact when your Husband is present. Be light and breezy and don’t respond emotionally to anything. Your Husband should be handling this mess, not you. If his family continue to be nasty, then let your Husband see them himself and you do your own thing.