Rose, the fear of the unknown is not uncommon. We all fear what we don't know. Change is hard because of that. I've been down the path you are about to travel, and yes it is scary at times... but it will be OK.
As for your husband, well, you know you didn't cause his disease, and you know you can't control it. As for "leaving him out in the cold" - I will tell you there are many resources available to those who choose to find them.
1. He can stay with friends
2. He can stay at the salvation army, for free. They offer help to people suffering from addictions, and destitution (again, not your causing).
3. AA meetings are free, anywhere in the USA. Perhaps the world too, I don't know.
4. As you know, there are many "self help" sites he can get support from if he participates.
5. He IS an adult and has free will to go or do what he likes. Adults can make their own choices and destiny.
Now you mentioned that he will cash in his retirement/IRA. Document that, as it IS marital property — you'll want to have proof of that waste of marital assets if you proceed with divorce. (If you are like me, or any other hard working adult who has worked hard to get what you wanted in life... (home, belongings, lifestyle)... you value what you've earned and deserve your fair share and then some.
Lastly, again... try not to feel sorry for him. Nobody put the bottle to his mouth except him. It was all his free will. We reap what we sow. This so applies to the alcoholic.
One more thing I'd like to add is: take one day at a time. Each day it gets a little easier, and soon you'll be out of the shadows and back in the sunlight!