Unfortunately I don't have any pearls of wisdom regarding your children, h and ow relationship - Its going to be hard for you and your children; this is uncharted waters for you all, I think you are negotiating them exceedingly well.
I know only too well how hard it is to hear about all the things your h is doing and who with, its like a twist of a knife in your heart each time. Remember that he is a kid let loose in a candy store, he is eating as many different variety of sweets as possible - but we all know how that ends ....one very sick child ....
Vge, you are one gutsy lady, you are dealing with so much right now, so give yourself a break and allow yourself to feel what you feel and know its OK.
Hugs to you, stay strong and stay positive that you will both find your way through the maze.
