Wow Jeff! I can't believe that this thing is THAT stuck. Ok lets get back to basics here:
Are you positive that you are on the right bolt? If yes, you said that you broke a ratchet on the bolt. Was it 3/8 drive? You can always go up to 1/2 for extra beefiness. Do you have access to a breaker bar? The breaker bar is a lot sturdier and should not break. Now for the WD40. Great for squeaks and moisture. Not great for freeing up parts. "WD" stands for "water displacer". We need "rust displacer". Lets spray it with something like PB Blaster. Let it soak about 30 minutes to an hour. Use the allen socket, extention, and breaker bar. That turd should break free! If you have heavy weld spatters like tfg did, you may have to heat it up to soften the spatters.
I know this is frustrating but you will be so happy when it all comes together and you have a bright flame dancing around. You have a rare case here, so we just need to overcome it. I think you'll be burn'in this week-end if you have time to work on it. Hope the storm treats you well!

That's the right bolt. Can you get any Blaster in from the front side. A trip to the store for a breaker bar around 15" - 18" might be necessary. And an extension long enough that the breaker can be held at 90° angle for better torque.