That area, where the manual crank nut is located is supposed to be packed in grease. On my unit, the nut was not that tight and since it was below the manual crank nut, it was greasy as heck in that area.
I put an open end wrench on the nut, then on turned the bolt with a ratchet from the other side.
But mine, as much as I'm beginning to hate it, has no rust on it like yours.
So, yes, spray some lubricant to free the nut.
Trailer: Lifted 228BH, heavy duty springs and Yokohama tires
TV: 2016 GMC Sierra Z71 4x4 CC, SLT
Spare TV: Two Alaskan Malamutes
Living somewhere in ID; previously lived in Moab UT; previous to that, don't ask!