Thank you for everyone's support. This forum has helped me immensely in my resolve that I am doing the right thing.
I am filing tomorrow. I am going to let him know with an email tomorrow night. While at first glance that may seem cold, I need to give him the space to digest the information as I do not believe he is seeing this coming even after everything that has happened. And I need to be able to form my words on my decision without immediately being met with his refusal, denial, anger and attempts at bartering. Of course I will talk with him when he is ready and willing, but I feel like this is the right way to let him know.
I'll be leaving this marriage with my daughter, her safety, my career and nothing left in savings due to the financial drain of his "recovery", the cost of divorce, temporary spousal support for him and full time child care for my daughter. But I'm OK with that. I'm buying control of my future and my life back. It's no longer up to him and his decisions on how I feel day to day or left up to him on how long it takes before I can feel safe, secure and sane again. There is a lot of relief in that.
Don't get me wrong, it's heart breaking. And I'm sure he'll claim this last go round was his "rock bottom", but I am done. And I am finally at peace with it. I may not be at times during this process, but I'll be ok.