Did you record / edited the audio yourself?
Because the soundscape was easily the best part for me. (Even if not, great sound sourcing and sound design)
I wasn't able to get anything but the medium ending.
I tried dispatching all phantoms and then kill the intruder and killing the intruder as fast as possible while elimination only 3 or 4 phantoms on the way. I also tried shooting him in the head and in the heart which did not seem to have any effect.
Using a gun on the intruder felt a bit weird, I guess too real, compared to the supernatural phantoms. But that might just be me.
Overall a nice and atmospheric experience.