By moving folders, I was able to restore the Hack Slash Mine saved worlds, and some of the Tekkit / Tekkit Classic games. Some of them aren't working yet, so I might try your suggestion of creating a new world and copying Level.dat and Level.dat_old over.
I also found out that /technicssp/ is for "Technic SSP," a modpack that is broken and removed.
Have a good week!
Paul