Artistic/workmanship question: I noticed the head is a bit askew and the left side of the mouth is pulled in significan...

One thing I learned from working on an animated movie production is how often things are cheated. Character rigs are frequently pushed really far, to imperfect places, in order for the animator to get exactly what they want from a specific view. All that to say that if you're trying to 'xerox' a piece of artwork - like this lesson is specifically about - you're going to have to accept that it won't be perfect. The biggest reason is your 2D source is most likely never perfect. But it's become less frustrating to me over the years. While I'm a die-hard perfectionist at heart, I'm slowly learning how impractical perfectionism is. I agree that this lady's head is a bit askew in the end, but overall it's shaped well enough for me to accept it. With this 'xeroxing' approach the tension lies in balancing accuracy to the artwork against the 'good-from-all-angles' 3-dimensional-ness of it. How you strike that balance is up to you as the artist.