Six years ago his heavy drinking was acceptable to you. And as the relationship moved along you assumed he’d outgrow it but as you are finding out that is not the case. You have outgrown him and short of him changing exactly who he is today (alcoholic) what you see is what you get.
Even if he were to actually have that deep desire to quit drinking and jumped into a recovery program……who says you’d even like him sober? All you have ever known with him is a man who has functioned with an alcohol soaked brain the entire time you have been with him. The times you assume he’s sober because he’s not consumed alcohol yet doesn’t mean he’s operating with a sober brain.
I would do lots of research on alcoholism, addict behavior, codependency and check out some al-anon meetings for you in your area.