Thanks for the thorough feedback! I had some apprehensions about that first room. The idea was to force players to backtrack past an enemy they already killed to teach them the enemy resurrection mechanic, but you are right that there are too many other rooms that are red herrings forcing the player to get lost/frustrated.
The lighting/stutters seem to be mostly attributable to it being a web build and runs more smoothly in the windows build. I'll have to do a balance pass looking at ammo quantity/placement and the key placement in that first room.