I absolutely love the melody and the basic form.
It seems like you occasionally hit a few notes that shouldn't be included in the harmonic structure... almost as if they were added *rhythmically* but don't belong chromatically. I don't know that there is a right note to substitute at those places and suspect that no note (sustaining the previous note) would work fine.
I keep hearing snippets of vocal lines in my head that could lay on top of this.
It seems like it could stand on it's own as an instrumental with the addition of one more movement that maybe gave the overall form a more defined sense of direction.
Thanks for sharing.
best regards,
mike