What a fool he is, he had everything right there in the palm of his hand and threw it away. He had the love and support of a lovely capable women and you have obviously done the best you can for him. His loss hun, I would say the classless female is welcome to him, let her support and care for him, which I very much doubt she will do.
You are blameless in all this, hang on to what you have, which will be a lot more both materially and emotionally with him out of your life.
I have no doubt that other people have worked through this type of thing, but ask yourself this, is he worth the hassle, what at the end of the day can he offer you. Certainly not the love and loyalty you deserve. It is devastating right now, that feeling of desperate loss and hurt, but you will get over it and come out of it the other side, hopefully with people in your life that are worthy to be there.
Chin up, head held high,
Suzie xxxx