The "Dark" route starts with a photo choice, then with some cake.
Nothing dark really locks in besides those two choices until a big event that is listed around "Day 69" or so, if you play the game efficiently.
In that "Day 69" event, you will be given a choice of "Hero" or "Pimp" and it will make all the previous choices have more impact on everyone involved.
You can change routes for the cake option later, but the other is locked in.
So just choose good route (avoid "Dark" marked options).
As far as Wild/Mild those simply change dialogue from vanilla to kinky but do not affect the outcome.
The first 68 days or so, MC is just learning the job and discovering people. Having loads of sex after a youth of loneliness.
In addition, the game is intended to be dramatic, funny, and tragic to some extent. While serious things happen, please try not to take things too seriously.