I think we're given these shocks to push us forward in our own emotional healing and detaching. The thing you feared most, came true. I also went through some similar things.
The best thing is, once you face it, and really keep talking to yourself that you are better off, you are emotionally detached.
I promise you, this will be for the best for your emotional healing. I know it. It will be painful at first, but you will see how much it pushes you to the path you were meant to be on, and heals you and opens your heart to someone new and better. If you were still hung on H like this, you could not make room for someone new in your life.
You will have love again in your life. Better than your H. There will come a day when you thank him for leaving you, and you think back to the pain, and look in the face of the love of your life and say "ahhhhh, THIS is why I went through that pain, to finally see what real love is....and for that, I will do it a million times over."
I will tell you this again and again. You are so much better off without your H, from the things you told us about him. SO MUCH.
You keep assuming he is some wonderful, caring, deep and amazing man.....as if he has faced his issues of infidelity, emotional retardedness, and all that. You assume he is the man you wanted him to be all through your M.
HE IS NOT. He is simply with someone who will take him as he is. You could not. Nor should you.
So, they will likely be happy, because they fit. They match. They are each others type.
You are amazing, deep, insightful, have grown, beautiful, and intelligent. I know that from knowing you here. You have grown and will continue to heal your self-esteem to finally be at a point in your life where you choose a man worthy of you, the right man.
My love to you.
Consider this a blessing of sorts.....finally, H is totally unavailable for you to move forward without looking back.