Yeah, maybe it's time to have a little chat with guy friend about giving out any information about you to the alcoholic, or reporting conversations with him to you. He may have meant well, but you can tell him that you are doing your best to stay OUT of his life, and that these conversations upset you. You can tell him that "how you are doing" is none of the alcoholic's business, and what the alcoholic says/does is none of YOUR business. The one exception would be if the alcoholic says something you NEED to know for your own safety (e.g., that he is stalking you or planning to show up at your house unannounced).
Actually, the fact that the alcoholic is walking by your apartment, looking at the windows to see if the light is on, is somewhat disturbing. Does he normally have reason to walk by your apartment? If not, that is potentially a form of stalking. If it disturbs you, you can apply for a protective order/restraining order. Or you could ask your friend to inform him that you are creeped out by it and that he should stop--which could give you a basis for a stalking charge/protective order if he doesn't stop.