Well, identity is a big theme. Caleb is constantly trying to define himself in fanfics. Another theme is the struggle between right and wrong. He has made some morally ambiguous decisions, so fanfics often explore how he grapples with that. Also, the theme of love and friendship. His relationships with others, whether it's a romantic interest or just a deep friendship, are often central to the plot of the fanfics.
Well, you could try reading the first few paragraphs carefully. They often set the stage and give some clues. Or, ask someone who's familiar with the type of story for some tips on what to look out for.
It could be her family. Her parents, if they are understanding, might step in to help with the baby so that Tris can still focus on her studies to some extent. Or perhaps an older sibling who has been through similar situations or is just very caring.
No, usually not. In a well - structured story, the interactions are planned to happen at specific points during the story progression. Vivec, being part of that story world, would not be available for communication before the tale begins.