Some very minor tweaks, of most important note is that I carved away the right side of his cheek some to give it a more natural shape (cheeks rarely encompass the eyes, eye sockets are a very large recesses that tend to leave gaps between brow and cheek as I've done here) and I removed and changed some of the colors on the hair.
I also tweaked the ear, which was shaded very darkly despite the light source coming from around where it was.
There's other minor stuff like some chin tweaks to sharpen his heroic jawline, but hopefully you get the gist of it!
I'd say your proportions are fine you just need to look at some comparable faces to try and figure out where to shade some more. There's plenty I left undone here due to time issues, but I'm sure you can figure it out!
