Ive got a 96 disco, that recently decided to leak all its brake fluid out of the front left caliper. I picked up a replacement caliper, and attempted to swap them today. I took off the wheel...and thats as far as I got

Heres my problem:
The two nuts that I need to remove to get the caliper off are completely corroded/rusted onto the bolts. I circled them in red.
I tried spraying it with this every 15 min for about an hour. Also used half a can of wd40. I scrubbed it in with a tooth brush.
After hours of that, neither nut will budge, and the socket is just rounding them off. Is there anything else I can do? I REALLY dont want to take it into a shop and pay $100 and hour for such an easy job. I have a plasma cutter, but im not about to go cutting into that and end up hacking off half the bolt. Any suggestions? I just dont see what else I can do other then torch/grind it.
Thanks!!