After all this, can I ask, do you have a bootable Windows 10 USB stick, Yes or No?
If you do it is a easy fix, if not then I suggest you make one.
You can of course boot from some Linux, copy your files, re-install, copy them back and so on but honestly an in-place upgrade from Win 10 to Win 10 worked fine for me and it is easy (as long as you can boot from USB or DVD).
EDIT: I'm not saying don't copy your stuff like @simrick said just an in-line upgrade would be an easy solution after all the usual backup stuff. I did it a couple of days ago (post 7 ) and it worked out fine for me. In my case I wanted Windows to run the upgrade compression which it doesn't do on a clean install.