This reply is a bit late since your original post was months ago yet I did not get around to viewing this thread until the date stamped on this reply.
There is one suggestion that may be of interest to you. The face looks a bit narrow compared to the photograph. I would use the "Transform Layer Content" option found in the "Edit" menu (or Ctrl+Shift+Alt+T) and stretch it out just a very small bit to get closer to the fullness of the face in the photograph. You will then have white space on both sides of the image that can be adjusted using the "Selection" tool and the "Rectangle" option to choose the corrected size and then select in the "Edit" menu the option "Crop to Selection".
I think you will be pleased with the results if you are looking to come as close as possible to duplicating the photograph using digital painting tools and skills.
On the other hand I could be wrong with your intentions, you may have intentionally decided to make the face appear narrower in your drawing?