I don't know about making human models, all I can offer is my lame person who has seen humans his entire life perspective. He looks flat but that's because you took the screenshot in orthographic view. Also looks like his mouth and chin are way down there, like it was pulled down. And maybe the face feels squished from the sides to the center. Remember making humans in 3D is the holy grail, it's no easy thing you are attempting, it's going to take a lot of practice, so keep going.
Well, The course is far from finished. Here is the teacher:
(I have to start over. Something is wrong) 
It looks like the problem is with the face, it looks narrower than the head.
If you look at Kent's model, the cheek bones are slightly wider, or as wide as the head.
You should be able to use the grab brush and pull the face wider, trying to keep the proportions correct.
It will take some practice and adjustment of the brush size to get right,
so I suggest you save at this point so you can go back and keep trying until it looks right.
I can go back. I used uncremental saves. The eyes are too small. Thx for the advice.
