The 3 C's:

You didnt cause it.

You can't control it.

You can't cure it.

Alcoholism is a disease, you can't talk someone out of it or convince them they are drinking too much. It's a compulsion.

Regarding spotting it in future relationships, be very careful. Ex-partners of alcoholics (usually a codependant) will alot of the time attract another alcoholic or addict.

Was he drinking when you met him?