1.) You should direct your questions about the topkiller plugin directly to the developer in this topic:
http://www.bigbrotherbot.net/forums/releases/topkiller-plugin-1-0-4/ perhaps he's aware of the issue. This is a third party plugin and not supported by the dev. team
2.) In the xlrstats.xml file you can set the minimum level for the command. Set the levels in this section to your liking:
1
2
60
As you can see the topstats command is for regulars and higher levels in the default config.
3.) B3 only reads logs, keypresses are not logged by the game engine, so they are not visible to B3, hence B3 can't parse your request.