I can't say how it is where you live, but where I live (the Netherlands) I would say you'd have to pay for the drinks. Or at least offer to do so. If he refuses than you know where stand.
Personally I wouldn't find it weird if someone suggested they pay for my drinks, I'd be happy and accept the offer
Brainstorm about what you what you want to ask, maybe using a "spider web approach" (circle with some words in it, connected to other circles with words in them, connected to .... don't know the official term, but it's a great way to organise your thoughts :))
Make sure you get (most of) the answers you came for. Some people (and artists more than other, no offence) tend to talk-and-talk-and-talk.
You need to take the lead (not forcefully, be polite!) in the interview.