Midlife For Dummies is funny, once you've detached and gotten on w/your life. You can actually go back and say, "yep, that's exactly what happened". They all have some sort of excuse for leaving and many of the excuses make absolutely no sense to us, but to them they do. It's very said.
Just remember, his crisis is about him and there's nothing you could have done to stop it. You didn't break him, therefore you can't fix him. Life has a way of working things out and you have to have a lot of patience and hope.
You and your girls are doing fine and will continue to grow and thrive as you walk the path of self discovery.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.