Congrats on the Brown! Not an easy accomplishment. I think you went up against a brick wall with this image. A super wide angle lens is going to have a very difficult time demonstrating a shallow depth of field, even wide open.
Neat car and perspective! But depth of field seems pretty deep, not shallow at all. Try zooming in more and using the widest possible aperture on your camera. That will throw more of the background out of focus.
Very cool shot. Looks like it's hovering above the ground. The slight fisheye appearance works well for this. However, though the background is *slightly* out of focus, I think this is not really fitting the challenge theme. As far back as those mountains and trees are, the DOF isn't really shallow at all, and what there is of the effect is not being used in a manner that adds any interest to the composition. The effect seems minor and incidental, so I expect you are getting creamed big time with DNMC votes.