I know you realize that this low feeling will pass soon enough. I'm glad to hear that you're still thinking about all the options for you and your children. I agree to a point w/what Karen and Kev said, but there is a big difference between "running away" and simply "moving on" -- not to be read as "giving up" if you're not there yet. You've always shown good judgement when making these decisions, and I have no reason to see why this would be different.
I do agree w/Karen about your GAL'ing - do it for you - not to get any sort of reaction from your H.
Have you ever discussed the possibility of a move w/your H? From the way you describe his interactions w/the kids, I don't know how much emphasis he puts on spending time with them.
Extra thoughts and prayers for you today. This too shall pass...