I finally understood how to play.
My overall gameplay can be resumed in: 8 priority people, 1 murdered (she was the "death by violence" cause), after the 10 people mark all the deaths were by illness, final population of 3 people and around 14 food left (I had more food than population since day 7 even by giving extra).
Farmers, workers and merchants are priority. The firts day people are going to die even if everyone has foodt them die.
Once population is lower than the food you have you can start to be a little humanitarian (if you still have soldiers, children, students or unemployed by then).
If people says they can pay you for an extra ration you'll want to have at least twice the food of the population to give a yes, and it's prefeerable to stay between the 2 and 3 total rations for them; if they insist keep saying no, they'll eventually leave, no need to kill.
But also beware of the "unemployed", if you keep getting deaths by violence it's probably them, and not necessarily the adult ones. There was this Darcy girl who I didn't give rations until day 4 and she always stole an extra ration, once I got fed up with her I shoot and after that deaths by violence stopped...