He's leaning back too much, which is causing a bunch of run-on problems.
His ear is too high, too big, too far forward.
The base of the skull at the back of the neck is too high.
His neck is leaning back, and there's not enough meat filling it out towards the front.
The face is too flat, the cheeks and the outsides of the occipital lobe are not pulled back enough.
My paintover is a bit rough, but you get the idea.