I am unable to remove, what I believe is a Gorilla brand wheel spacer from the rotor. The screws are pretty rusted and my attempt at trying to unscrew it resulted in failure.

How am I supposed to remove this thing? I don't have a wrench or socket big enough to fit the hex nut in the middle. Thanks in advance.

 

The large nut is to secure the axle, not the spacer. The screws are used for ease of assembly at the factory, so drill them out, and use a lot of PB Blaster, then hit the spacer on the flats all around the studs. I usually put the lug nuts back on over the studs to protect the threads just in case of a misaligned hit. Some might suggest heat, but unless you're careful, someone might go wild and damage the bearing with excessive heat. Might want to also try a sharp chisel at different areas behind the spacer, just don't go wild and try and drive it in.
It's not imperative you replace the screws as the wheel will hold the rotor in place.