There are some things best left to professionals. . .
With air tools. . .
To at least free up the stuck bolts.
Run them up some, down, and back up to the same point.
Before I had a compressor, I would take FWD vehicles to service garages and (offer to) pay them to loosen hub axle nuts. . .which they usually would do as a courtesy, when I had a bad axle to replace.
I think you are working against yourself at this point.
Those bolts have to be tightened first, to pull the threads apart from themselves.
Right now, they have been sitting against tension for so long the threads have probably compressed and started to bind.
You snap a bolt and you might end up being one unhappy camper with broken teeth.