Is it the nut itself that won't come off the stud? I would try penetrant like WD 40 over night. I can't see how it could cross thread when it was already on. Going by your SuperStart transfer, it is the last of the full cranks which has electronic ignition, just before the cheaper to produce Powertorque series.
Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!
