You have no choice but to remove him from your life. A person with an addictive personality will always find something to attach it to, be it alcohol, drugs, gambling, overspending, the Internet, sex, etc.
Addictions are a symptom of deeper problems, usually with their source in a person's traumatic childhood. People look for things to fill major voids in their psyche, voids which were not filled by a family filled with abuse, lack of love, abandonment, alcohol, etc.
Before a person can get over their addictions, which they use to numb the pain of their past, they must recognize and address the suppressed anger and resentment they feel from those early experiences. The process is long and arduous.
By sticking by someone who has issues with hair on them, you become a codependent and simply exist to feed into the issues of the dysfunctional person. If you want to read more about this syndrome, use a good search engine like
www.google.com and enter terms like "dysfunctional family," "adult children," "addictions," etc. You'll get more material than you have time to read.
Staying with somebody like this will be a certain dead end. Once he recognizes and acknowledges his problems it could take years of therapy, reading and hard work for him to completely heal and become a fully actualized human being.
You could suggest he seek counselling or a support group for his problems. There is probably no better organization for dealing with this kind of dysfunction than Alcholics Anonymous, with its twelve-step program. However, it's not likely he'll do anything until some major negative event (such as you're leaving) triggers him to seek help.
Don't feel sorry for him. Every man is the architect of his own destiny. You worry about yours.