I'll try my best to answer as many of these as I can ...
First of all, surprised there was a posted line on a Stetson - JMU game. The Colonial has been a posted conference for at least 15 years, but didn't know that was the case with the Atlantic Sun.
The TN Tech - Central Florida and Samford - Murray games are easy to answer. All four are from posted conferences (C Florida C-USA, other three Ohio Valley).
The top 20 or so of the 31 conferences that have automatic bids to the tourney have lines available for all games, so any games involving two teams from those conference will have a line available. When MU is playing someone from below that threshhold (off the top of my head, Hillsdale - D2, ND State - United, UMBC - American East, Delaware St. and Morgan St. - MEAC, Oakland - Mid-Con, Savannah St - Indy) there won't normally be a posted line. If someone in Vegas or running a site thinks they'll get equal action on the game beyond the posted conferences, they can post their own line, so if you try hard enough to find a line on a game involving a team from outside the top 20 conferences, a lot of the time you'll be able to find it (what seems to have happened with the ND State game).
For some background, the numbers of posted conference has steadiy increased from about a dozen to 20 over the past 10 years or so, due to more games being on TV and the Internet, which increases wagering interest on teams from the mid-majors. If MU is playing someone from outside a posted conference, a lot of times it's not worth the books time to post a line, as there's an inability to get equal action on both sides, and the possibility that a smart guy who knows more about the small team than the book could take advantage of them. Most local guys are taking their lines off the Internet.
