1. You are better at this than I am, so please take everything w/ a grain of salt.
The biggest problem with this, for me, is that it doesn't have a clear focal point. I suppose the head, in its entirety is the focus, but you probably want it to be the face & eyes.
I would darken the background color behind the back of his head a bit to lessen the contrast behind his dark hair and the bright background, and similarly darken his ear a bit.
You might want to ad some harder edges to the ear, as it's going to be somewhat of a focus, no matter what, due to it's high contrast area, and it's position as the most foreground element. I'd do this after knocking it back a bit though, as it might not be necessary.
I'd sharpen/add details to the eyebrows and glasses, and maybe throw in a specular on the eye glass arm, or glass to pull the viewer's attention there.