It's the guilt and the MLC pain that's driving your H. He's lashing out because he doesn't yet understand that the pain and unhappiness are coming from within himself. The only way he will ever figure out that it is not you causing it, is to let him go.
It's human nature to want to hurt someone that's hurt us. Fight this impulse. It won't do your cause any good to talk to the ow at this time. What it will do is build a triangle consisting of her and your H and giving them ammunition against you. It will be giving them a bond and something else to do besides them getting to know each other. I know it's counter intuitive to do this, but as long as your H is bent on being with her, let him get to know the real her. She knew your H was M and she stepped in between anyway, let him get to know the real her. Let him find out and see what he's lost in you and that you're the better option if you decide that is what you want.
DU, this is not something that will be a quick fix, this will go on for a long time. Get your game plan set and buckle your seatbelt. Decide what it is that you really want out of life. If you let it be this time can be a gift to you. It will show you what you're made of, the things you want to change and how you want to proceed.
It doesn't seem like it now, but you do have the power, if you can center yourself and remain focused the opportunities will present themselves.
Keep trying to detach and I know it's hard, but it will make you feel better. Eventually there will be more days that are good than bad.
