If you delete your GamerProfile.XML file, it resets all your settings to default...even the Display settings.
Mine is in: Documents>MyGames>Watch_Dogs>user-id*>GamerProfile.XML
When you start the game it creates a new default GamerProfile.XML
* - my user id is a bunch of numbers/letters and yours will be different than mine
Not trying to bring up and old thread, but I found this through a Google search and figured that people could benefit from this info. Especially since it was unsolved.
Apparently watch dogs is one of those games with PC NOT in mind. It appears they dont have a reset button for all the settings, you are just going to have to experiment and see what works it seems.