The lower ball joint on that truck is "loaded" so you have to "unload" it to check it for wear. Jack placed under the lower control arm itself as close to the ball joint as possible will push up on the spring and that will unload the lower ball joint. Then you can check the ball joint for looseness. Make sure the jack is in a good spot by shaking the truck a little before you put your hand under the tire to shake it. You can also pry up and down with a pry bar under the tire. The control arm is not flat there and they are little tricky to get the jack in a good spot.
Front to rear tire rotation is preferred here because if one front tire is causing it and you swap them side to side it can feel the same and mislead you.