I think I see what threw you off for the skull. Skull 5 is a drawing, and it looks like they made a few mistakes on it. I would recommend trying to find multiple views of the same skull. That way you get consistency across all views
This is hopefully what it will look like, on the top view it wont show much of the skull but just the hair, while the window will show the full skull more
Update. Had to shave down a few parts of the skull because it kept poking through, eventfully deciding to just turn it off (the skull) and work on it (the face, with references).