Sethellic
I’d say yes to part 2 and 3 if you keep your main elements close to the horizon line.
Things get distorted and confusing when you extend far above or below the HL as you can see in the linked sample:
http://billmelvinart.com/pictures/box/persptest.jpg
The square below the HL is distorted because the viewer’s line-of-sight is not on it. It is along the HL. The square below the HL needs 3-point perspective, which would not work in the same image with the square above it.
The reality is perspective drawing is an idealized approximation of what is really going on within an image. This problem occurs in 3d apps as well that do not have a true lens distortion camera feature based on focal length.
The bottom line is you have to cheat, here and there, to keep things believable.
I haven’t seen the DVD but heeding Mile Dream’s suggestion may be a good idea:
“if you want to understand perspective drawing top to bottom, get Scott Robertson’s DVD”