You can tie a knot and hide it in your batting so the loose end at the center isn't a problem.
The stitch length is determined by the machine speed and the speed you move your fabric.
The FMQ foot may just barely touch the quilt. It should be very easy to move around.
If you'd like some great tips, look for Leah Day either on You Tube or her personal site. She offers great videos for beginner to andvance FMQ.