Hi Artist,
I’d say, practice more…I had to start over 7 or more times, before I was halfway happy…it is not easy to get this right, but on the positive side, once you have your base right (Chapter 1), things get ‘easier’.
The head looks different in perspective and Orthographic….Yes, that’s normal:

It also depends on how zoomed in you are and your View Focal Length (50mm by default, if I’m not mistaken)…
Mirror doesn’t always work exact…there is a Symmetrize option in the Mirror dropdown menu:
rr
It really doesn’t sound like your doing anything wrong, just practice more…You’ll get there!