But they said to adjust it until I could barely see the darkest icon.

It wouldn't help anyway, seeing as how the sun is out 24/7 and the skies are clear.
Can't form a logical response &--#62; automatically resorts to calling someone a troll.
you want a logical response? Fine then
The game is dark and gloomy, there is murder, half the city has died from the plague, whats left of the population is infected many of which to the point of becoming weepers, all the while a dictatorship has formed and is ruling the city through the use of force. On top of this events of the game involve things like poisoning people, assassination, and child abduction. One level even takes place inside a brothel.
Characters are also extremely dark and are often referenced to either be sick and dieing (or in many notes in the game dead), plotting to kill each other, hiring assassins to murder each other, trying to break out of a corrupt city, betraying others for personal gain, tortureing others, along with some characters expressing desire to kill themselves.
As for modeled after Victorian London it is. That doen't mean exact replica. It was based off victorian london, whaling cities, and their own designs mixed in as the devs have stated.
Also you claim you just kidnapped the royal physician but then reference it having no effect on the Pendletons. Newsflash. The Pendletons mission is before the royal physician one.
As for it being day 24/7 the 2nd, 5th, 6th, 7th, and 9th missions all take place at night. Less than half of the missions take place during the day.
And regarding atmosphere as mentioned. Half the city dead, a good chunk of the rest dieing, corrupt and dicatator-esque government, murder, etc. That is a very dark atmosphere. Add in aspects like many of the notes you can find lieing around, the immense amount of corpses before you ever show up, and the heart and the atmosphere is extremely dark.