1. David, what's the point of having motor nerves fire action potentials that are not enough to fire the muscle? How is it different than firing no action potentials at all? Is this regarding the body being on the verge of moving but still not yet moving?
Yes, it is preparing the structure of the body for movement. Not just the muscles but the whole body structure ( muscles, skeleton, connective tissue, skin, etc ).
One way of teaching the Aikido demo of unbendable arm, other then ki or water flowing from your finger tips, is to imagine reaching for something out of reach without moving. When you do this you can feel your body preparing to move. This strengthens the structure of the body in the direction of movement.
Try the unbendable arm reaching for something out of reach with both arms in opposite directions.
Here is some more opining from some"enlightened ones" of the "New Age" from Harvard Medical School.
While this is about the structure of the cell, the body structure is organized similarly.
A short interactive animation of the cell as a tensegrity structure.
This is from the 'Children's Hostpital Boston'.
More information about the tensegrity structure of the cell is here,
at the 'Ingber Lab' website at Harvard Medical School.