No-one WANTS the person they are with to leave, not even when you know they have to go, that they are hurting you or could really physically harm you. None of us want that. It's like admitting defeat.
Thing is OP, it's not OUR defeat. He failed you, as he failed his former wives. You are hanging on to the hope that YOU would be the one that succeeded.
But this is not about you, not in the slightest. For some warped reason, this bloke you are married to can't allow himself the luxury of being settled, happy and content. He clearly has self esteem issues and feels unentitled to be happy, so will set about destroying every relationship he has.
The harder you try, the more he will fight to prove himself right.
You can't help him, you can't change him, you can't make the slightest bit of difference. he pressed the Destruct button.
You now have only ONE option, to get yourself and those that depend on you, to safety. His brooding presence in your life is stripping you of dignity, self-esteem and hope.
He needs to get out.
He needed to get out before christmas, last year, and probably before that too, but that is in the past now.
Your H and this Caroline have similar partners in you and her H. You blame HER (your text pre-christmast to tell her to back off) and He blames your H (by telling you that ALL contact from your combined quarter is unwelcome)
You were let down by your H. He's not thinking about HER H.
Caroline did the same to her H, not you. You don't figure in her thoughts at all.
Get your focus right, take control over your life, your home and your dignity.
If you allow him to pollute your environment until he is ready, and her H does the same, then there IS a big change that they are planning this.
So wreck the plans, tell him to go TODAY, that he is being unreasonable and cruel to you by staying and that you deserve some space and peace to work things through.
He needs to go. A decent man would go.