UPDATE: Took a little persuasion but it (the axle) eventually popped out. The broken stud came out easily with an impact wrench. Now I just need to get some Moser 3" threaded studs and I'm back in business. It looks like the Weld lug nut failed and stripped. I wonder if I should switch brands of lug nuts, but they are Weld wheels. I ran a thread chaser over all of the other studs and removed any bad spots.