Mixed feelings
I liked the semi-original chord progression... not often do you see a progression of 4 minor chords... however, the melody did not mesh with the chords in the background... Your melody kept on wanting to play major chords against the minor chord framework, and you can tell that the two are not working in tandem with one another. The strings are not very consequential; in the course of the listening you can kinda forget about them.
The second variation is a bit odd... very pop-ish (in a musical sense, like, say, Castlevania or the like) and not exactly fitting what you would call the mood, feel or structure of a nocturne. It's not bad (though once again the bass and treble fought with each other), it's just not a nocturne, you see?
The final section once again had a few dissonant minor seconds, which I liked, but the major problem (ha pun) is that the melody wants to be major, while the bass is minor. I'm not saying to change the melody, but it's clear in the piece's composition that it was begging for a different makeup than the one it had.
So as it stands, I have mixed feelings about this one. On one hand it's cool, but not really a nocturne. On another hand it's nice, but it struggles against itself too much.