i can't find the files that u are talking about...in the scripts folders i only see files for visual efects and such...nothing for player_vs_npc damage....
You need to have Notepad ++ to edit the Xml files and to understand xml format. But you can also use notepad2 to edit the file. In the scripts folders are files that can be edited. I don't have it installed right now so all i can say is search the files to edit them. open each one and look for the above info.