Actually, non sequitur means “it does not follow”, in other words the thought does not logically proceed from what has just been said. In this case, Caulfield just doesn’t realize that it follows perfectly.
There’s barely a TOWN in Rodney, Michigan, let alone anything else. I’m not sure what Jef’s referring to here, but I don’t see why it would be that. Could be a friend. (I went to school with Jef from 3rd grade through high school.)
That would be Big Rapids High School, Big Rapids, Michigan, from which Jef (and I) graduated.