RE the ext HD, I was going to suggest you move your game save file to it, disconnect it and then delete the file and the associated Cloud file that it syncs with. This would bring your game back to when you first started but with all updates installed. From what I've seen in your video, it appears that there is nothing wrong with the game installation nor the patch installations leading me to conclude that one of the save game files is corrupted not allowing a proper sync. You can't delete the cloud file without deleting the local file (thus losing all your data) but you can delete the local file by itself and then the game will automatically create another local file and resync so your data is not lost. The external hard drive idea was so that you could backup your local saved game file & keep your data.
Have you tried deleting the local file only and if so did the sync happen when you restarted the game?
Because you can play under another username seems to confirm that synchronising the save game files is the problem.
