1.) It was used as an example of pointless side stories overshadowing main plotlines, so it's probably not even going to show up again because he KNOWS IT AND HE WANTS TO TORMENT US SUCH THAT WE RECEIVE A GLIMPSE INTO THE DARKNESS OF HIS WORLD.
2.) Maybe it could go places, in which case I support a broadening of "everybody belongs to Sensei".
3.) I'd rather see more of Komori and Chie.