Re: Producer wants to talk... now what?
The only thing I would add is that, one potential goal of this meeting is to agree on a vision of the project that he would produce that you would be enthusiastic about.
The best version of this meeting is one where you're just completely on the same page, and every note he says you think is great, and inspires you with interesting ideas that the loves. Needless to say, that's not super common, but it does happen.
The thing you want to be careful about is saying "no." I've literally been in a meeting where the producer asked a question, and my writing partner said, "No," and you could feel the air go out of the room. And it was frustrating because it was a note we could have worked with. "Yes, and ..." is your friend.
eg., in that specific case, the producer talked about the idea of romance between the preteen leads. And what we should have said was, "Yes, and it's really a romance about power, not sex. He feels powerless in his life and he's drawn to her blah blah blah."
And what my partner said was "No, it's not a romance."
In my opinion, the gap between what we wanted the script to be was much smaller than the gap between the words we used to talk about it. They didn't want a script about preteens making out and neither did we.
This doesn't mean agree with everything he says. But if he says something you have a visceral reaction against, things like, "That's interesting. I'd have to think about ways to make it work," or "I like that idea but it presents some challenges like X, Y, and Z" are responses that keep the conversation going and make the producer feel like you're working with him.
You don't have to have all the answers. You do want to sound like someone who wants to find them. And sometimes you can't end up working with someone, but don't assume that's the case just because they give you one note you dislike, and find ways to keep the conversation flowing.