I wish to comment on Question 3 Signage.
I think two distinctly different signs ought to be set up. One with a wheelchair picture and on with a cane. Each sign should designate whether the trail is paved or not. And then the difficulty. Flat trails could be designated by a straight line. Slightly difficult (steeper) ones with a rising line. Moderately difficult ones with a steeper line.
Explanations of these symbols could be posted at a parking lot entrance to a trail.