I just played and rated your game, as well as left some feedback on your game about what I think is specifically good and bad about it. But for the purpose of this thread, they can be summarized as such: atmosphere - good, repetition - bad, frustrating abstract puzzles - bad.

Beyond that, though, I think your question hints at a misunderstanding of how horror works. It's not the things in the game that make horror scary. It's the overall situation and progression. For example, in your submission, the situation is a person, assumed to be somehow like the player due to no further context, in a room that gets reset with them in bed every minute. This is obviously a dream of some sort, but it's one that isn't about anything in particular. It's just a room with bad acoustics. From there, the situation just repeats with the room arrangement making less sense each time. There's no reason to believe the situation is going to get worse.

If you put in blood and guts in the same situation, it would only help initially. Then the situation includes the question of why the player's room would have blood all over. However, unless the player can find a reason for the blood, the situation would then return to just being a dream of some sort, because the blood is just another random element of the dream

Now imagine instead if the dream featured a plain room the first time, but with each repetition another thing is added to the room that makes it more unsettling. The first version could be just the room. The second could have a stream of blood coming from behind the dresser (raising the question of what the dresser was used for). The third could have insects coming from under the bed every 5-10 sec. The fourth, fifth and sixth, could have another random thing is added, with the seventh or eight repetition starting to layer the unsettling elements or increase their frequency (so that you don't have to make an infinite number). This would allow the player to start imagining not just what it is that is actually going on but also how much worse is it going to get.