Can I remove/install the bottom ball joint without removing the top? Long story short, the nut was the wrong bread pitch in the lower ball and seized on the threads. The Allen stripped in the process of removing it. So I had to cut it off and now need to replace it.

 

Yes if you have the correct tool, or hire one, you need a universal ball joint removal kit something like this, it has lots of option to fit your ball joint if you need to you can use it to remove the top too, as it best to replace them both

now click on the link and watcha video to see how it done, now if you only want to remove the lower one just use the tool as shown when he does the top one, as the way he removes the lower one is not the normal way to use the tool, it should have had the threaded bar underneath,