If he wants to move out, let him. If you try to stop him, he'll want out even more. Let him see that you'll be fine, and keep blossoming.
Remain positive. And start being positive not as an "act" in front of your Husband, but because there's a ton of great stuff in your life you are doing for yourself.
Try bellydancing...maybe karate. ;-)
By the way. Talk to your lawyer and see what his moving out means in your state vis a vis custody, and financial settlements. Him moving out is stupid legally. Is there anything you need to document...etc.
Remember Karen...you need to pace yourself and take care of yourself. I'm in the home stretch right now, the affair is over betweeen wife and OM, but I didn't really care for myself as I should have, and I have little energy left for the relationship.