Easiest way to edit perks like that would be to use the convenient PerkEditor in the Tools directory.
Wait nevermind. I can't get it to do anything other than Strength. There's probably some easy fix.
If the PerkEditor doesn't work correctly for you, directly edit it from perks_data.fos. More Criticals is #309.
Around lines 124-135.
The "5" in 14, 1, 5, // Critical Chance increased by 5
is what the value you're looking for is.
I tested it in-game and it works. Change 5 to the value you want.