Your husband sounds like another fellow on intervention that I watched.. his name was Lawrence. He owned his own business, sipped on vodka too, most of the day.. and never seemed all that drunk.
You might want to watch that episode, here's the link to part 1, the other parts are on there too
YouTube - A&E Intervention - Lawrence Pt. 1.
I was the drinker in my relationship, and I drank vodka 'all day' too. I went to the ER once with a .568 BAC, after the doctors got over the shock that I was alive, they also were freaked out that I was walking, talking, not slurring etc. I have no memory of that. My body should have given out on me. If I kept drinking like that (a 5th a day) I would have been dead within days, my doc told me. Regardless of how alcohol effected me and how I acted, it was quickly killing me, and would have.
For the record, mouthwash contains much LESS alcohol than vodka, it's just a desperate form of alcohol for many alcoholics. It's around 27% alcohol.