WIll I ever be able to go back to Whiterun in skyrim after killing the Guards?
You never respawn in Skyrim, the game reloads to the last save, so your bounty will naturally not decrease. You should eventually be tracked down by a bounty hunter and get the chance to repay your bounty + 20% for his troubles. It should, but is not guaranteed, to fix the problem. The death of the jarl could be problematic in the long run, however, if he is indeed dead.