I have read that spraying with a 3-5% hydrogen peroxide is supposed to improve incubation hatch rates. I wouldn't wash eggs, though - the ones I've got in the incubator now arrived really dirty, and they still are. Don't want to mess with their... whatever... natural protective coating. The one that went bad... whew. I hope I never have THAT happen again. At least I caught it fast - it was only incubating four days. Everything else seems fine, regardless of grime.
I kind of wish my cracked egg were showing any signs of having life in it, just to see if it hatched! My pecked egg hatched - Wren, my little Silkied Serama. Maybe that's what happened. Her egg got pecked, and it scared all her feathers.