you can either pin or baste your quilt and backing to the leaders- some people find basting to be faster- some of us just pin-that is a personal choice.
to stop-start just take 3 or 4 tiny stitches in place then begin your lines that secures your threads. i clip them off as soon as i'm a couple inches away so i don't have to worry about catching them later.
as for the pole height- i really don't know- mine are where they are- there is no adjustment to move the bars- i don't quite understand how that works, so can not help.