I would think that an upgrade repair is your best bet to recover your current OS. Looking over the other post that you referenced, you've already tried that. That indicates to me that something that you have installed, like this keyman.dll, is interfering with the OS. That fits with your comment of "explorer works if I boot into safe mode". I'd suggest uninstalling that software and any other 3rd party software that might hook into the OS at a low level. Then try the upgrade/repair again with the latest ISO download.