I definitely believe that kids can pick up on the emotions of the people they rely on to take care of them. Security, predictability and daily rhythms are so important to little ones. Those are hard things to come by with an active alcoholic in the home.
When something is up to upset their sense of security, children will react. When one of their caretakers is unavailable or upset or... they will react.
Continue to be the great Dad that you are, Shellcrusher. Make sure your little guy knows he can count on you by continuing to provide that sense of rhythm (your bedtime routines, etc.) and being available physically, mentally, emotionally, for him.
Wishing you peace and continued strength.