Boundaries, what about not seeing him if he is drunk?
Also my humble advice is therapy/Alanon - given your dad is an alcoholic its possible you will attract one as a partner... I don't know, what about asking the guy to stop drinking altogether? in my humble experience any normal person will give up drinking if the partner asks for it. Hell, normal people don't even have alcohol come up as a TOPIC. So to me that would be a good test. If for whatever reason I was hurting someone by drinking I would have NO issue not drinking at all anymore. If after this request he resents you, keeps drinking, tells you YOU are boring, or whatever then........ he may be an alcoholic, just in the early stages........
Well anyway one of my main sources of support has been a therapist with experience in codependency and addiction. My life has improved, not only the romance area. Hope you can find one.
All the best.