This is a complicated situation. I had a co-worker who reeked of alcohol when she spoke with customers & a few people commented on it - so our boss was within his rights to say something to her. She denied having a problem & claimed the smell was from the night before. She was never inchoherent, but had blood red eyes and slurred at times. (We could never figure out where she kept her stash, but knew she must have one.)
My boss was afraid of the ADA - since alcholism is considered a disability & alcholics can't be discriminated against. Surely if they're missing time, not performing, & not pulling their weight, there's a way to get them to seek help. It does sound like this person is almost hoping to be let go. What a dilemma.
It's good of you to care, and he's lucky to have someone who's been there, who could really help. It's a shame he doesn't take advantage of it. Please do let us know what happens.