• go to the directory of Jedi Knights and then into \GameData\base
  
• open the file "autoexec.cfg" or create it
  
  • this file will automatically be executed when the game starts
  
  
• add these commands:
  
  • seta sp_language "0"
    
  • seta ui_iscensored "0"
    
  • seta g_dismemberment "3"
    
  • seta g_dismemberProbabilities "0"
    
  • bind "insert key of choice" "g_dismemberment 3"

This will:

1. change the language of your game into English
   
2. remove censoring of your game
   
3. enable the most of dismemberment
   
4. set the hightest probabilties for dismemberment
   
5. bind the command to the key you entered

The last thing is necessary because the game disables dismemberment after loading but with the binding you can easily enable it again without going to the menu.
You probably can omit the 3rd line and just rely on the binded command but better be safe than sorry.

You do not have to activate realistic lightsaber combat so that every enemy just dies if you touch him with your lightsaber! Though you might want to active it because you have an even higher dismemberment rate then. You then would have to add:
seta g_saberrealisticcombat 1

If you want blood you could go with this one:
http://mrwonko.de/jk3files/Jedi%20Outcast/Mods/Mini-Mods/81937/