For starters, you're dealing with a typical ball joint. Same technique goes for control arm ball joints and outer tie rod ends.
Notice the taper. Tightened down, that thing wedges in there HARD. I'm surprised by your predicament. Hell, I've never heard of it happening. The typical struggle is getting the damn thing apart. I use a pickle fork.
Hopefully that helps make sense of my suggestion to cinch it back down first so you can remove the nut.
Maybe try giving it a whack from underneath to get a start wedging it in. Don't want to do that with a new one but this one's toast.
Also to wedge in tightly, you actually want the opposite of lubrication. Try rinsing it out with some brake cleaner before tightening.
Let me know what you think.