Yes, i agree with you about the face shadowman. It looks like my drawings when im 13 years old or so, it looks terrible. (At first it looked ok, but after a time passed i realized it
)
About the lightning, as i said earlier, the only shading i used was in the cloth, and that was minimum.
About the light source: Yes, i agree with you, again. But especially with these kind of drawings, you can imagine a lightsource and draw as you please. Some people use that and some don't. It's a practical thing, because there is no model to work with that you can use as a reference.
The grey lines are not shadows, people generally draw them only to find the true shape (or making it 3D etc). I found it annoying when i first heard it, but if you are new (with that mouse, yes i'm new) it really helps you. I just did not erase them. (too lazy...)
Overally though you have a good perception, and i seem agree with you mostly. and dont be sure that you cannot draw with mouse. I expected worse when i started to draw this, but it looks at least normal in its own way.
@Xyzzzy: I dont know. Maybe i should add colors. But that would spoil the whole comedy element of it
The lines with black color were finished in 15-20 min. The grey ones were finished in 5 min. or so. Then i saved it as JPEG and realise it really darkened it or something. Then i saved it as PNG and erased the grey spots around the lines. (which took another good 5 mins 
They must be done before the shading, but after doing them i dont bother with it, i was bored already. If i were to use shading, many of those lines would be erased.
