Can I use any Linux live distribution to boot into my system and change the file for run level and set it to a valid run level when it has been set to run level 0 or 6?
You should be able to change the run-level, as the default run-level should should either be set in
/etc/inittab or a sym-link from
/lib/systemd/system/<target name>.target to
/etc/systemd/system/default.target. Booting from live means you ignore the installed OS entirely and use the live OS instead, but can still access the hard drive.