Yep. Vertical E-Track.
Yep, that's why its there.
Yep. I use it for that also.
My floor is made of a plastic composite sold at Home Depot as fascia. Comes in 12' lengths, 8" wide and ½ thick. The stuff is heavy, but very durable. I'm guessing it adds about 60 to 70 pounds more than 5/8...