At this point, I'd head to Sears and get an "impact nut/bolt" remover. This is for use on an impact tool, but would most likely work with a breaker bar. The best way to describe the tool would be a conical spiral of flutes. They have several sizes and are cheaper by the set (around $20). I've used them personally to remove the locking lug nuts when I've either lost the key or the key broke. A rounded lug nut should come off nicely with this tool. If you have a heavy duty 1/2 inch air impact wrench, all the better.
If you live in the Orlando, Fl area, stop by and I'll remove them for you.
