To start this off, I'd like to say my congratulations on this piece, as it's pretty impressive. With such an imaginative theme there were a few areas you excelled in and a few that were a bit wonky.
The opening is well done in how the sound effects are merged into a mass of storminess, and it creates a nice cinematic feel. There was one weird bit at around :59 where an effect cut off abruptly, but apart from that the first minute has very few issues, as I see it.
At 1:15 and a few bars after, there are two bleeps that are a little jarring, but it might work if their velocity were lowered and drawn out (perhaps with a fade-in / fade-out). As it is it adds to the atmosphere, horror-movie like, but stands out a little too much.
The piano that entered shortly after had a nice melody, but if you're looking towards an ambient and atmospheric song it might be better to use a softer synth with additional length. I generally just connect my synth melodies so that they flow well (legato). If you intend on keeping the melody then you could also manipulate the sound effects (that you used to create the creepy feel of the music) to have chords that matched.
The entrance of the drums gave the sound extra tension and fit relatively well with the music. Even so, maybe you could lower the volume or even remove the tuned percussion that accompanies it? Personally I feel that they seem too dissonant if compared to the piano and the background sounds. Generally, in dark ambient / atmospheric music you need to sacrifice certain melodies and synths / sound effects just to keep the balance. Having the volume of a repeated sound effect increase or using a change in rhythm should help maintain the intensity and the mood.
Sorry this is so long...
But overall this is a great piece, but like any song, needs to be fine-tuned in certain aspects.