I mean, it’s not like I’m a horror expert. I actually try to avoid those for the most part (yes I’m weak, so I’d have to refuse the prototy, sorry).
All I can talk about it from a game dev perspective. In a horror game, imo you want to evoke a strong emotion in someone. Usually fear, but you can heighten that response with tricks. Like humans don’t like it when someone is jumping on them, that’s why I suggested a zoom in. The light flashing is also an attack on your eyes/brain and would be perceived as threat. All of these small things add up. However, some people will call that cheap, and it’s not like it’s the only thing. I assume a better way would be to prepare their subconscious by doing slight shifts of visual or music. Show them things that are out of place. Even if it’s subtle, players will pick it up subconsciously and will be on alert, which is what you want. You want to have a build up of tenseness, that you can then break it up with a jumpscare.
Again, I may seem like I know what I’m talking about, so take this with a grain of salt. I’m sure you can find better resources for this.