Chris,
Yes this one is the 500lb model. As far as a pattern it basically throws a 180 degree arc and yes the rate is adjustable. There is a chart on the spreader that gives you a pretty good idea of rate per acre at a given mph.
My wife really pitched in again today as she always does. We're clearing a path through some woods so the horses can get to the new pasture and she clears the brush and tree tops as I fell the trees and cut them up. Those locust trees with the huge thorns can really be a pain in the you know what.
Ken, yes the back of the spreader is a little flatter than the rest. I can't really tell if that is the design or a shipping problem. Either way, it works just fine.
Kevin