Notepad should suffice to edit. Notepad++ is better if you do a lot of modification, and free.
AI Handicaps is a different beast that you don't want to mess with for this purpose.

Sets what the AI gets, not what you get.
You really don't want to be editing that file in the steam directory, as that's the base game, not the mod. The mod will overwrite whatever you set in there anyway (assuming the mod edits the values you change, which in this case it does). Plus when/if the game is patched or updated, your changes would be overridden as well.
C:\Users\XXX\Documents\My Games\Sid Meier's Civilization 5\MODS\g_k_enhanced_mod__v1_13_4\GEM\Barbarians would be the directory. GEB_End.sql would be the file.
Right at the top, there's a line of code starting like this.
Code:
UPDATE HandicapInfos SET EarliestBarbarianReleaseTurn = 100, BarbCampGold = 100,
All you'd need to do is replace the "100" after BarbCampGold, for each difficulty to whatever preferred value. I could definitely see how with raging barbs and honor going, it's an overkill button early on.
Keep in mind whatever you set it to do, it will be 3x that amount on marathon. Marathon 3xs many ruins/camps rewards; did you try it on a different speed as well to see if it was lower?