I'm sorry you feel like an idiot. YOU ARE NOT!! You made what you thought was a good decision based on NOT seeing alcohol abuse and that was good. Now that you have discovered differently, you need to make a good decision to let go and move on.
This is a fairly new relationship, it's in that getting to know you faze and now that you know, he's just not the one for you or your children, this is what dating is all about.
When we fall hard so soon for someone, discover things we don't like about them and look to change them.........that's when we know it's OUR issues at work not theirs.