10 years ago he had problems with alcohol.
10 years later he still does.
none of us are powerful enough to MAKE someone unhappy or FORCE them to drink. how he is is how he is.....before you came along and will be after. he has shown you that nothing has changed....he drinks and bounces from woman to woman.
you are right. this is a toxic relationship. also a dangerous one.....he is a loose cannon. and if he aims his own anger and frustrations at you, you are likely to get hurt, eventually. physically injured.
you are out. now stay out. he is not going to magically change into a wonderful person. he's the same guy who broke your heart and behaved badly a decade ago.