Just listen is very good, I think if he asked questions, like what should I do or what do you think, I believe I would say, "Gee! I think your AA people would be best to help you with that, as they have been there."
Just my thoughts. We have to go with our gut.
If he sounds positive, might be good to say something like "you seem to be doing great."
I have always heard, "Don't work their program for them"
My personal words I hate to hear are, "You should" or "You better" .
Advice from program people will be taken without feeling as if it is personal.
If one mentions 90 /90 probably be nice to not say "You should", rather say "the 90/90 suggestion sounds interesting, probably lots of different people and more ideas and information".
These just my thoughts and suggestions.
Take what you can use and leave the rest, and keep coming back. Do you go to Al-Anon??.