Really? I have to do all that crap just so I could do the quest? Wow. Good job Bethesda.
I agree, it is a bit much to expect us to go to all that trouble because they cannot get their game to run properly. You are trying to get your game to run a bit better than it currently is, it has been played for a while and it seems to need a bit of spring cleaning. There is no specific bug with the quest that is preventing you leaving, it is a problem with the game not being able to load the area, which is related probably to the same problem with it being unable to autosave for some of us. Whether it was that loading screen or another it was going to eventually get you. You go to all the trouble of clearing the game cache, uninstalling everything and reinstalling and downloading the patch and all the DLC, you get to play Skyrim and the DLC a bit longer. It comes down to, how much do you want to continue playing Skyrim.