V,
Remember this really isn't a discussion, as he is not going to talk you out of it. You are stating a fact, we are in separate bedrooms for a year, your on and off drinking for the last 20 years, I am unhappy and I want to move on. Done, period.
I know its a lot easier said then done, but it really isn't open for a discussion. If it gets escalated, tell him I'm sorry, its how you feel.
Good luck!!