New
#11
Yes DISM fixed it - good news :)
SFC replaces corrupt things from the component store. This was also corrupt so sfc could not work. Dism fixed the component store and this meant sfc could then work and replace whatever was wrong.
As for how often to run probably only if something is not working is it required. It would not do any harm to run every week (or every day) though. Perhaps after installing upgrades would be a good time.