Thank you for writing this piece. You've really managed to create a dark, 'last waltz' kind of feeling and atmosphere. The combination of oboe and guitar adds to this feeling I think.
I am no expert on writing for guitar, so maybe someone else will have something useful to say on this.
What I do feel would add to the intensity of the piece is a contrasting middle section. Right now it is only dark, and I think contrasting it with something else (rhytmically, melodically, or harmonically) will bring out your intentions with the piece even more.
Example of this (contrast starts at around 1:20):