I've been away from the boards for about a year so I could be wrong on this. We have been playing that if you force a grappler to move that breaks the grapple.
1) Should the grappler be able to make a Str vs. Fort check to keep hold of the grappled?
2) To Otterscrubber, If you have the movement, move into the square you want the grappled opponent, then move back to your first square and drag the opponent. Depending on where they are and you want to move them, it may take three squares of movement and two drags.
3) In Ferghis's example, grappling and dragging the Mezzodemon would break the grapple (or some other push/pull/shift). Your unconcious ally is still vulnerable there though.