How much more clarity do you want from him? He decided he no longer wants to be in the marriage, and took the steps to fulfill that choice, and you were notified. That's been communicated pretty darn clearly!
I think it's time for you to focus on the rest of YOUR life and your wellbeing. I wouldn't blame all of his shortcomings on being an alcoholic.. it's possible that he just doesn't want to be married to you anymore, as blunt as that is.
Course, that could have everything to do with him being an alcoholic, you're getting in the way of his drinking himself to death-plans.. be happy you're free from the front row to that circus.