Chuck,
Our previous coach was a '99 Fleetwood Bounder 34V with the F-53 Chassis and the V-10. Nice coach. Lots of room, well built, always dependable. Sometimes I wish we still had it. Anyway, yep, been there done that on the parking brake issue. Sometimes, disimilar metals can do that. They can "freeze" up and, you have one hell-of-a time breaking them loose.
If I may make a suggestion. Go find a can of "Freeze". It's very similar to those little butane bottles that one uses to refill small butane powered items like lighters, soldering guns and all that. Only it's not flammable.
Anyway, here's what I did in a similar situation. I heated the immediate surrounding area around the bolt, with a propane torch. Not overly long, just got it good and hot. Then, put the propane torch down and, applied a liberal amount of "FREEZE" directly to the bolt head, for about 3-5 seconds or so.
That bolt spun out of there almost without a wrench, it had shrunk so much. IT's worth a try anyways.
Now, just for your information, in case you might be interested, here's a photo or two of what mine looked like when I removed it and rebuilt it, even when FORD said it was NOT REBUILDABLE!
Scott
P.S. Incidentally, your unit is actually called a "ZF" parking brake.
I also have PDF breakdowns of how the different models are put together/shown.