Anyone with any automotive knowledge can clearly see by the pictures you've posted, you used the wrong socket, there is no contact remotely near the center of the lug nut, just the face. Why would you strip all 5, if the first one didn't work? All you needed was a 17mm from the looks of it, or maybe a 19mm thin wall socket, the same socket that 'Presumably the shop that installed them used' if you buy the correct thin wall socket, from the pics it looks as if you shouldn't have a hard time getting them off, regardless of how much you already stripped the face...