I would highly recommend
getting the latest binaries and set up a more recent build of the server. That version hasn't been updated in ages, and is missing a ton of options, not to mention an outdated database.
What you could then d is change the
Character:ExpMultiplier in rules_values to what you desire. There's also the
Character:GroupExpMultiplier,
Character:RaidExpMultiplier values to change as well.
Almost forgot, there's some editing needed in the guide, and since I can't edit the post, you might want to check
this topic for people reporting issues until I can get the guide up on the wikki.