I have played it several times know and i must say that you made up a really, scary game.
Are you trying to do it similar to the real article?, watching that you are using the original face of 087 brought my curiosity
More than one monster would not be a good idea, but getting different forms to show up our little friend could work pretty well, since you are using corridors and rooms like SCP 087 B I could suggest a event were the player is in a room with 3(or more) corridors and 087 pop up from the dark and he start to go backwards into a dark corridor, making the player to think twice if he wants to go that way (you could make this a tricky one, in the corridor there´s a chance of 087 still being there or not, so noone can really be sure if this cool guy is in it or not. Perhaps the player could get on a situation were the only way he can go on is taking the corridor that 087 got into)
Also, diferent forms of death, maybe one could be that after 087 reach the player, he drop the camere, and the spectator can see just darkness and a little bit of light comming from the flashlight, and then the face can be visible in the dark, gets closer and then the camera get a fast static noise before shuting down.
Finaly, i would suggest a little of psychological fear, the player start to alucinate, watching the face of 087 when he is not present in the room, slow footstep that make the player think that 087 is behind...
I would love to help on this project as much as i can