I don't touch type, but I do use more than two fingers (three on one hand and two on the other normally, with the right thumb for the space bar & the left little finger for the shift key). I don't need to look down at the keys too often these days.
I do tend to rest my palms on the built-in wrist rest on my MS natural keyboard, or on the flat area in front of the keyboard on my laptop. Either is better than resting them on the desk, although I know I really ought to have them hovering above the keyboard like a proper typist.
Probably the worst typing position I have used was 20+ years ago when using VT100 terminals for programming - the keyboard connected to the vdu by means of a long curly cord, and we found you could lean back in the chair with your feet on the desk alongside the screen and the keyboard in your lap whilst programming... which, of course, we all did whenever the boss wasn't around. Green screens, flourescent lighting, no windows - too many years of that is why I now wear glasses!
I know what you mean about holding the mouse button down for extended periods - that's why I insist on wheel-mice these days (I found myself doing it whilst scrolling through long documents or web pages). I've used a Wacom tablet - they're great for any type of drawing/painting work, but I find them unnatural for anything involving lots of clicking. It's probably just me...