[scottz]

That's ugly. A couple of ideas come to mind.

If you are not comfortable working on it or don't have the tools, your best bet is to find someone to come out. Talk to a truck stop that has a mobile service; they can probably get it off.

Do you have a welder or know someone? Grind off a little of the chrome and tack weld the adapter in place. It will be tough with so little clearance to the wheel.

Disk brakes or drums? would it be possible to pull the whole spindle off?

I assume it is striped out completely, if not, you could tighten it and break the stud off. That's a long shot.

Take a die grinder with a cut off wheel and cut a slot in the nut that a big chisel with a hex handle will fit in (like a screw driver). Use a wrench on the hex handle. Looks like there might be enough room, but I suspect the nut would break.

Last option, pull off the other seven nuts and use the wheel as leverage to brake it.

In all cases, I would put some heat on that nut before trying to turn it.

Most likely, you are going to damage that wheel, but not a lot of good options.

Good luck and let us know how it works out.