Heat heat heat heat till the bolt is red hot. Then splash on lots of cold water.
All those ticking sounds are the sounds of rust frozen fasteners letting go.
It should come right off after that.
If it still refuses after that then the penetrating oil will work a lot better because of the cracks that have opened up thanks to the heat.
I have usually been able to get somewhat rounded nuts off like this with just a handheld propane torch.
