Great stuff man. Keep it up. I really like all the proportion stuff you're doing. They really show improvement. Your SPs are getting better too. On the last one, I think the eyes and nose show good observation, but the mouth still looks like you didn't "see" it. Next time don't draw the shape of the lips you see, draw the shapes of the shadows and highlights that define the lips. Then fill them in with the values you see and erase as necessary. Also I agree that a softer pencil would make the shading easier and would help you increase the contrast.