great stuff mate.., but i'd be looking at the shading and depth of the 'hat'.., there's no 'fall off'.., dont be scared of the 6B (and make sure its sharp )
for sure portraits are not easy, i used to do them but they became so photo realistic i began to think.., why not just take a photo..?? really!!!! there was nothing there that was.., 'me.' I believe there should always be a little 'style' in a portrait .., some character/styleing.., maybe the lines, maybe the dynamics (shading).., whatever.., something that applauds the artist and gives a little 'more' to the subject.., if yu know what i mean
dont stop mate
take it easy and life will be easy