It was explained many times on MS Forum. to repair install, and since Windows XP this feature has worked, and been explained.
take the USB insert it and run setup. or if that scares you uncompress all the files on the USB to your user Download folder in a folder called ISO. run the setup from there and follow instructions. it is easy, it does work,
you never said if SFC fixed and issues or had more to fix. many times system files can be corrupt and windows will still run. Not perfect but will run,
many different things can be attempted, to try and fix this issue, since it really is not know what exactly the issue is.. all we can do is simply try to fix. The first thing is we have to insure that Windows is in top shape. with NO ISSUES. then to try and fix all the other stuff. then we need to have a pretty good idea on what isin you inaccessible system. (Programs, malware, AV, trojans, cracks, hacks, and if you have allowed any thing via exception to stay installed. What 3d party programs do you have installed, are they all genuine or patched.
a nice program to assist in this is BelArc, (FREE) then save the scan to a txt file, then zip the file so you can attach, and members can see what you have so as to assist. It also will check and give you some idea