[De'vID]> Can {ler} be used to mean "oscillate", like for a usual pendulum (with the pivot at the top)? Or is it only used when the pivot is at the bottom? Also, would a regular rhythm like that of a metronome be described as {lerchu'}?

Yes. {ler} can be used for "oscillate," and it can be used for a pendulum regardless of whether the pivot is at the top or bottom (or somewhere else).  And {lerchu'} could be used for what a metronome does.  Maltz was glad you asked these questions, because they reminded him of another word (and helped clarify the meaning of this one).  The other word is {lav}, which can be translated "lean, incline, slant" and so on.  It means something like "move to a slanted or angled position." The starting position is often, but doesn't have to be, upright or perpendicular.  If it's a person, the person's feet stay put (as with {ler}).  And, as with {ler}, the pivot point can be on top (or somewhere else). The difference between {ler} and {lav} is that {ler} is used for continuous swinging, back and forth and back and forth (forward-back-forward-back, etc., or left-right-left-right, etc.), while {lav} means motion in one direction only, then the motion stops (though the stop can be very brief). Returning to the upright (or earlier) position is {lavHa'}.  For both {ler} and {lav}, the direction of motion doesn't matter (left, right, forward, whatever). 

[De'vID]> Can I assume that {much} is used not just for commands, but also statements? For example: {lol SuvwI'; mIl'oD much}.

Yes.