You have added tone, shading and highlights. If you find you need highlights on his hair, cheekbone, nose, above his lips, within his lips -- you can do it by your kneaded eraser that you can shape to a knife-like point. Try drawing highlights with it. You will gain fantastic results.
You have given your Carlisle tone, added deeper shades to the sweater to look more like the picture. Since you've worked so hard on this picture, pat yourself on the back and file it away to glance back when you have grown more in drawing.