A couple of quick questions:
Hit points for level 0 guys: it’s banging around my head that Level 0 mercenaries have 1d6 hit points, and level 0 non-combatants have 1d4 hit points, but I can’t seem to actually find that in the text anywhere. Where is it listed?
Dexterity: I know my players are going to ask why Dexterity bonus doesn’t apply to thief skills, it doesn’t, does it?
I don’t think there’s an official answer in the book for your first question. I usually give all level 0s 4hp, since it would be odd for a level 0 to level up to a theif and lose HP.
As for your second question: the benefit a thief gets from high dex is they level up more quickly, meaning that if two thieves start together and one has a higher dex, they’ll frequently have slightly better checks than the other.
0-Level Humans have d4 HP. I’ve never seen anything about them having 1d6 (though I do miss things) if they are combat trained.
This is why Beastmen are so scary, and Kobolds aren’t really ‘weak’ (they are as tough as mundane humans and fight better than they do).
0-level humans have 1-4 hit points, correct.
Human military troops of 0 level are assumed to always have maximum (4) hit points.
In D@W: Campaigns we explain that at most 3 peasants per 10 families can be conscripted into a domain's military and militia, which is to say 3 troops per 10 adult men (each family has one adult male, one adult female, and three children). These three men are assumed to be the most able-bodied, in the top 30%, so they have 4 hit points.
Peasants and laborers generally have 3hp, sedentary humans have 2hp, and children and elderly have 1hp.