The best (and quickest) way to fix this is to reformat your SD card, reinstall LibreELEC and *cough* restore your backup.
Apparently you already tried what could be tried, and still the errors keep on coming.
I'd say: admit defeat, because sd cards will corrupt from time to time. Keep a good backup when things are running okay for occasions like these.
Yes, the easiest way to fix an SD card is to format it. Before that, if you still have access to your SD card data, you need to make a backup, otherwise you have to use a data recovery tool to recover the files in the corrupt SD card.
