I'm unfamiliar with DarkFAIL, I avoid it like the plague. Ithian's guide doesn't cover the proper way to uninstall V1.1 of DarkFAIL. In theory, it should replace any Corp IOS with a regular one... in theory. Why don't you try what I suggested --- overwrite, don't uninstall the existing 58.
So I dowload ios 58 v6176 with nus downloader and install it with dop-mii? Do I need any patches?