Chown root mistake
Solution 1:
Did you tell it to recursively apply it?
You may find that it did not apply it recursively in which case only the top level will be userx:uxery so you don't actually have to change anything except root:root again.
If you DID NOT chown -R then it should still be fine.
Solution 2:
If you did your chown recursively:
On a comparable distribution, start this command:
find / -type f -printf "chown %u:%g %h/%f\n" > /tmp/myperm.txt
In the rescue mode of your system source myperm.txt
after you chrooted to the root directory of your mounted mess to chown the intended files, this time :-)
This will at least set something correct on most of the files.