This has good production value but the music itself doesn't communicate "nightmare" to me. The track almost feels like it's coming from a place of inner peace. It's entirely too mellow and has more of a calming effect on me than anything.
My advice would be to change the overall mood of the song to a darker tone. Alternatively, you could use what you have to give the listener a false sense of comfort, then kick them in the face with some truly nightmarish sounds.
Adjust your aim and take another shot at this track. I think it deserves it.
Please contact me if you would like to use this in a project. We can discuss the details.