Take the car home on stock wheels, and put your 18's on yourself. Those guys are being a PITA.
You'll never beat the inner wheel houses in with a hammer, unless you really want to tear some sh!t up. You'd have to crush the upper trunk floor to accomplish this.
You don't need 1" of clearance either. 1/2" or so is just fine. Unless your rear bushings are totally worn out.
Get it home, and post some pics. They'll work.