On your questions 6 and 7, about mapping software and clearances. There are applications for commercial trucking that would probably work. Although they are a bit pricy compared to something like Streets and Trips.
We have used PCMiler where I work in the past, they seemed to like it. They put out a package called CoPilot without all the freight rating functions.
CoPilot
I also found ProMiles. I've heard of it, but don't know anything else about it.
ProMiles
-lee