Wow, I can't imagine my mom calling me and telling me that my career plans that I discussed with my parents may lead my Dad to drink again. If he would drink that easily then this is a failed attempt at recovery. Didn't cause it, can't cure it, can't control it....and also can't control what other talk about.
Is there more here to the story? You mentioned that sometimes it feels like he is hanging on by his fingernails - do you see red flags for relapse? What kind of a program is he working? Is he in a 12 step or is he just attending meetings? What about you - have you attended Al Anon?