Great voice! Drums up, and maybe, give the drums a little more to do? You are clearly going for something minimalist here, which is nice as well.
A couple of passes on the guitar maybe? It's a great mellow progression, and well played, and maybe there's a d string that moved a little flat in a passage or two. Won't be noticed by the majority of listeners.
It all hinges on the voice, and the feeling of the song, which is very strong. To be able to sing like that? Great stuff, you should feel extremely satisfied with that vocal performance.
cheers,
-Tom