1) Is the door gap at the front correct/can you loosen the hinges and move the door forward slightly?
2) When you jack it up from the middle or one end does the gap change much. There will always be a small change, but if it's a big change you need some combination of new sills/floor/floor stiffeners (although a Frog door gap should get bigger at the top when the flor is rotten)
3) Otherwise, grind a bit off the edge of the door, weld it up again, spray it :eeek: