A while ago, maybe even the first thread as I read your story it didn't seem like it was alcohol that makes him want to leave, and now we find out it wasn't. The guy for some reason or another is tired of being in your marriage. He seems selfish and not worth wanting to keep; especially if he already has another women. As others have pointed out, however, you focus on you!
If I remember correctly you said you didn't have a job, it is the perfect time to look for one. Consider being healthy as a means to being sober: join a gym/health club facility, or simply walk around your neighborhood. Your mind will think clearly when your out walking
Pick up some hobby: painting, reading, exercise, etc. Get your mind off things; it's his divorce after all. Life doesn't always workout the way we want it to so expect the worse and prepare for these things.
All the best to you and your children.