Try changing to Treso nipples, use Remington caps, and make sure there's no cap debris between the hammeer and the frame. Uberti's mainsprings are generally strong enough to pop a cap.
The wedge should seat to a point where the spring's catch just snaps up on the right edge of the barrel lug's opening. Farther in can bind up the cylinder, and too loose opens up the endshake too much, and could cause the misfires you're getting.
Try VTIgunparts, make sure of the brand before ordering, Uberti or Pietta. Extra wedges is always a good addition to your gunbox, as are all the springs, especially the hand and trigger/bolt springs.