just echoing what others have said. most likely in a bind. stuff like this normally means mean getting out a long bolt or something along with a mini sledge / large hammer. and beating the pin out. even with things are greased up. when stuff is on a bind. it is just plain difficult.
just brainstorming. if you have some jacks or cherry pickers / engine lifts, you might try pushing things around that way. i always have the ugly long 6 footer pry bar as well.
if you can get stuff on nice concrete surface, you might try creating a "dolly" some lumber with some wheels on it. or setting bucket down on a pallet before trying to remove it. makes things easier to un-attach but also putting it back on at a later date.
for the old 1954 allis chalmers CA i have. one of the connections for hooking up stuff. generally requires a long bolt and a hammer to initially tap pin nearly all the way through. then a pair of channel locks, or pipe vise/clamp thingy, or like to twist and pull the pin rest of the way out.
a reminder. when turning off tractor, once tractor is off, hit all the joysticks / levelers for FEL and 3pt hitch. to remove any hyd pressure in the lines. and more so make sure everything is resting on the ground / pallet / dolly.
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it is risky, but having someone on tractor while it is running, and slightly moving FEL / bucket. as someone else hammers / pulls pin out. you might find the sweet spot and suddenly end up on your rear because it slide out so easily. (been there done that)