Reverse my steps meaning what? Re-edit the .plist, deleting the added line?
If so, I already deleted that file (the file is exactly like the original, not having the extra line inserted). So should I re-add the line, restart, delete the line, and restart again?
Also, I looked on another machine (that had not been altered). I did not see mDNSResponder listed in the Activity Monitor, I did see launchd though.