It's not you. Not at all. Alcoholism is a disease. It's never about you, however personal it feels.
Would I be way off base in thinking that there's some history of substance abuse or mental illness with one of your parents?
My dad is an alcoholic and my mom suffers from paranoid schizophrenia. I have spent a significant part of my adult life trying to recreate and "fix" these unhealthy relationships from my childhood with no success. No reflection on me, except my choices were skewed because I was gravitating toward what was familiar to me.
I think because you have no children or real ties to this second man,the best option is to let him go and begin working on yourself.
I attend Alanon meetings and individual therapy and am working through my childhood issues so that I can stop making these poor relationship choices.
Hugs and welcome.