How to fix Win Sys Corrupted Files

I run win8.1 upgraded from 8.0 via win updates. My original disc is for win 8.0. I ran an sfc scan and found that I have some corrupted windows system files (see scan atth). My problem is I cannot download fast as I have a slow cell tower connection. I was able to download the Win Media Creation Tool for 8.1 after four days and nights solid but then found out I cannot reboot from the usb unless I originally had 8.1. The update I think I need to reinstall is that dreaded massive update KB3000850 a massive 400 MB file which I cannot download.
How can I otherwise fix the win sys files without an installation disc of some kind while not being able to download an update?
I know it sounds crazy but I live in the Philippines and fast connection times are unknown here mainly.
I have not tried to reboot via the usb since I heard I could not. I thought I would check first and see if you think it will work.
Thanks, Dave

Hi Dave Leonard,

Welcome to the 8forums.

You may want to try DISM /Online /Cleanup-Image /RestoreHealth in an admin command prompt.
I'm not sure how long this would take with your internet, but the file that is needed for offline is a few times larger then 400MB.

If dism completes successfully, run sfc /scannow AGAIN.

edit- When I had a dialup connection I would go to a public library or local college library where I had access to fast connections & download stuff to usb.