Ball joint socket size and where to purchase?

The threads in your control arms didn't look too bad. Make sure you clean the old threads well, and use some anti seize. I'm sure you know this. but install the new ball joint when the upper control arm is installed in place.
Absolutely! That’s why I waited for the socket and kept soaking them in pb, a lot of suggestions to keep the control arms in place during removal and installation, and it worked well!