Hi and welcome,
Only he can tell if he is an alcoholic or not ......or how bad it is but many alcohlics do not drink every day (that's me) and can give up easily for periods of time (that's me)
I can't answer your question about alcohol's effect on sperm and whether or not it would affect a baby but I can tell you that your baby is likely to have a really bad life if its Dad is an alcoholic and it will get damaged, even if born physically perfect. Please do not think of having children with this man until you have resolved these issues. If drinking has already caused problems in your relationship, it will cause more.
There is plenty of support on the family and friends forum from people in your situation. Ultimately you need to look after yourself here.
take care.