Level Editting:
The size of the area you walk around is was nice! Not very big, but still big enough that I had to walk through a little bit of hallway. That's good!

I get the feeling you REALLY want to detail. And you're right details are very important, but be careful you don't detail too much, so that it confuses the player to what or where the important thing actually is.

Sound:
Great sound work. Lots of very fitting sounds. The walking inside the vents and such. Maybe the monster-sounds were a little bit too much, since you hadn't really seen a monster yet, so it's quite early.

Scares/Scripting
I liked the scare with the monster crawling towards you. It was very simple, yet I did get scared a little bit without it being a jumpscare. You may want to tone down the images fading in and out a bit. Maybe only show them once or twice. I got so used to them, that in the end I didn't really care the images popped up.

Puzzles:
The puzzle with the keycode was nice too! The way I had to search through the note was a good idea.

Maybe you should point out what is the ENTER key on the machine, because it wasn't all obvious.

Also, one thing that stood out: The keycode was never mentioned anywhere, why the room was locked, or why there were invisible numbers hidden in the room. You may want to write something in the note like:
"The requested explosives have been secured. This note should suffice as help for the code, should it be forgotten."

I think recharging the phone is a good idea.
Instead of running out of oil, you can always go back to that place and recharge it. I like it.

The game was laggy from time to time, I guess because of a lot of detail. I hope it'll work anyway.