1) What I have done for my Q&A is announced that I'm planning to do one. Usually I will make that announcement in a separate episode just in case someone doesn't read the author's note section. Then ask those to either comment or PM me their questions.
2)Then, I usually give everyone about a week or two to respond and then I will post the answers in a separate episode. I will either screenshot the question or just list the question in the standard body of text in an episode. Images can be added to novel formats via Firefox (more about that below). I don't include doodles since I'm not much of a artists, but I have included art before. That's something you could do though!
Fox Trap has it's Q&A at the end of the story, so you can check that out for a visual of what I did for that
https://tapas.io/episode/1522365
3) I've never had anyone complain about the placement of a Q&A, though I typically try to keep them at the end of the story. Readers can skip the Q&A if they want and continue with the main story. But I have randomly inserted art or a side story and no one has voiced objections to me.