I can certainly relate to your post, Cally.
My H did the same thing last October. We are now working on the M and things are improving everyday.
Not sure if you want encouragement at this time because you are probably feeling overwhelmed but there is still hope. I never thought we would be anywhere near close to repairing this M at this point but my H and I changed drastically during the S. I think S can be good for a M because it gives you a fresh start and also forces you to GAL.
I have two children and understand that they are the ones who pay the worst price. You did not choose this S, your H did. That may give you some sense of peace. I wish the best for you. Keep us posted on your progress.