I am so sorry you are in this painful situation, I know the word pain doesn't begin to cover it.
The love of my life divorced me a few years ago. Yes, a clause on that 'unconditional' thing. I understand why he did it, but that did not spare me the pain, frustration, sense of loss etc.
I know of people in a situation such as yours who have chosen to separate but not divorce due to their feelings about marriage vows. Sometimes legally or for financial or physical safety reasons that is not an option. I know of people who divorced their spouse legally, but in their hearts remained 'married' and chose not to marry again.
In time you will work out what is best for your situation, it's a process. Honor what is in your heart and soul, but do attend to the physical realities of living, which may include divorce. Even with a broken heart, we can do the necessary, if painful thing.
As far as dealing with his drunk driving. I personally feel that if someone is endangering others lives it must be addressed. I would want someone in that situation to do the same for me and not put myself or my loved ones in danger. A person's drinking is their own business, when they are endangering others it is society's business.