You have really put a lot of work on getting the proportions right - the amount of work you have put in is amazing!
my only criticisms would be the nose needs to be more rounded and show clearer definition between its different parts. I would look at different parts of the nose and construct from there. The position of the head your drawing makes it particularly difficult. I did a quick paint over to show what I mean -
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Hopefully this helps. The nose is the hardest part of the head for me. Because of how rounded its parts are and all its different planes i get really mixed up with it. Like I said though the proportions are spot on and your values are great.