Hello Confused. My suggestion would be to care of you and your kids and keep your mind off of him. What he does or doesn't do will not affect you as much as it affects him -- unless you let it. All this energy spent on him could be spent on you and making your life better. You can't save the world and you can't save him. You can only do what you can do to save yourself. I know it's difficult. It hurts. It sucks. Really sucks. If you were in the middle of a thunderstorm with lightning and floods and high threatening winds all around you -- would you stay in the middle of the storm and keep asking "Why?" The answer to "why" is not going to help you. It doesn't matter why. It only matters to -- get out of the storm.
When I went through some similar stuff that you're going through -- one of the things that helped me, was to visit with Al-Anon. They are really great in dealing with things like this. If you'd like to connect with them, here is a link to them: www.al-anon.alateen.org
I wish the very best for you and that's the best I can suggest.