I would assume that you've been at this long enough to know when he is drinking or exhibiting the behaviors of an alcoholic. The boundary issue is tough - we've all set boundaries, and tell our A's the consequences, but if we haven't followed through, they know these are idle threats. I am divorcing my AW because my boundary was no drinking and driving with the children in the car. This boundary was set after she had a car accident with the children, and a BAC of .33 on a Saturday afternoon. She went to in-patient, and lived in a halfway house for 12 months before she came home. She was truly offended when I told her it was over after she drove with the children 10+ times after drinking. I was convinced that she wouldn't do it, so every time I thought that she had, she would deny it, and I would try to figure out what else could be causing the behavior.
Don't worry about finding evidence that he is drinking. I gave my AW once last chance and it has been miserable, but now I can walk away with my four children and no regrets.
Good luck and give Alanon a try. It has brought me inner peace.