I'm not sure specifically what 'niku kyu light novel' is about as there could be many different stories within this. It could potentially be about various themes such as adventure, fantasy, or relationships. Without more context, it's difficult to say for sure.
They might be really surprised. Some characters could be amused by the creative scenarios fans come up with. For example, Hinata might be excited to see himself in all kinds of wild adventures in the fanfictions.
The characters might be a bit shy. For instance, if there are fanfictions about Tsukishima and Yamaguchi's friendship, Tsukishima might act like he doesn't care but secretly be a little flattered. Yamaguchi, on the other hand, would probably be more openly happy about it.
I have no definite answer. Sometimes manga series end when the story feels complete to the creator or when publishing circumstances change. So, we'll just have to wait and see.
No, there isn't. The main emphasis of Haikyuu is on teamwork, friendship, and the pursuit of excellence in volleyball. Love stories are not a significant part of the plot.
The Haikyuu manga is indeed over. It had a great run and left a lasting impression on readers. The story came to a satisfying end, tying up loose ends and giving closure to the characters' arcs.