Okay I just did this thing myself. Here is my suggestion:

Get the ball joint back into the socket (you can leave the bolt out for now), put the wheel on and lower the car to the ground.

Find a socket that you can spare, maybe destroy, and a short extension that you will destroy. Put the socket over the axle end and whack the extension with a hammer. The biggest hammer you have and can control. It will take a lot to move that thing.

Something I tried, not sure if it contributed at all the thing finally moved via the hammer, was to chuck a broken drift into a hammer drill. I that ride against the end of the shaft for a about 30 seconds. The hammer action might have helped.

It is easy to get frustrated at this stage, but it will move. The factory used locktite when they built that thing.

Oh yes, watch your hand when hammering. Of the 100 or so whacks I gave it, the axle that is, I did take one the finger.

When it finally moves jack the car up and the ball joint will move much easier.

Good luck!