This is exactly what I was looking for, except I can't find any of these settings in the CK. When I look for Skill Use Mult for an individual skill the way it's listed on the wiki i.e. Alteration or Destruction there's nothing under Game Settings. I can see Skill Use Mult but it seems to be broad spectrum coverage with a single Integer base.
Look in the Character tab, it is Actor Values. Anything marked as a skill can be edited to increase or decrease xp gain for anything related to that skill. You can also edit perk trees from here.