I want to increase the damage of blunt weapons by 10% (and reduce blades by 10%) but I can't find anything regarding these categories in the settings..

I don't think there's a global setting for that. I think the amount of damage is set on each weapon.

You can globally increase all weapon damage, but to make certain weapon types stronger, you'll need to edit each base weapon's damage.

Dammit. Is there ANYTHING simple I can do to make blunt more attractve vs. blade? It seems insane there's no values anywhere to modify something so central to the game.

Just make yourself a little mod that does it. Select a few of your favourite blunt weapons and bump up the damage by a couple of points. I recommend that you don't overdo it because they do a lot more damage as your character's skill improves.