I won't change the walking speed because I like it as it is.
About the enemy's damage: It's supposed to be a hard game, to frustrate the player, with permadeath, no medkits...
About the lighting: Yes, I agree it's maybe to dark, but I might not brighten it a lot, because to see the ghosts fading in from the darkness makes it spookier.
I tried to make an ammo system, but as I didn't have enough time and it wasn't working properly, I removed it. And it included fire rate, reloading...
And, about "how fast the gun can fire" it's a shotgun, so being able to shoot multiple times doesen't make a lot of sense.
However, thanks for the feedback!