I would most definately use some Xchocks between the tires and something a little more substantial than the plastic chocks in front of the tires. They are only good enough to keep the trailer from rolling a short distance while you hook/unhook. If a good puff of wind were to come along at just the right direction, the neighbors across the street will be getting a new trailer(from you)!
Big negative on using the refridge until you get it somewhat level. Of course you could dig out your driveway a few feet and level things out that way!
Also, the scissors jacks are in a bind(sideways) with the slope. I understand though, you gotta do what you gotta do.