First- - - -call your insurance agent and make sure your life insurance policy is paid up. You're getting dangerously close to that torque tube slamming down and pinning you underneath it, possibly with some of the vehicle weight on your chest. That's especially true if you have the vehicle supported on jack stands under the rear end tubes. You need to have the frame rails supported so there's no weight on the rear axle at all. One of my friends from high school back in the 1960's was seriously injured by the situation I just described.
Once you have that situation handled, scrape as much crud off the torque tube behind the knurled nut on the pivot ball as possible, and "shoeshine" all the rust off the tube with a piece of emery cloth. You can then unscrew the nut with a big pair of Channel Locks and slide the ball back to reveal the U joint. Before you unbolt anything, support the tube with a floor jack to keep it from falling as you unbolt the four bolts of the bearing caps that hold the joint together.
Jerry
