Hey Ramblingman

I'll do my best to answer the questions
1. My right hand technique depends on a piece that I play, some general rules are that the thumb is playing bass strings (E, A, D) and other three fingers play treble strings (index = G, middle = B, ring = E), good example for this can be
Evening BellsSometimes I play with thumb even on treble strings:
MalaguenaAnd when I play a solo line, I use alternate picking (index, middle)
There are two main right hand picking techniques: TIRANDO (free stroke) and APOYANDO (rest stroke)
TIRANDO, finger plays a string and do not touch any other string (remains in the air), this is for playing chords, arpeggios and melody lines that are not emphasized
Click to view attachmentAPOYANDO, after note is played the finger rests on the neighboring string, this is used for emphasizing melody lines
Click to view attachment2. It depends on the piece as well, if you play 4 string arpeggios than of course you need 4 fingers for that:
Etude in E Minor, for three strings arpeggios I use three fingers:
Etude in A Minor.
Regarding right hand pinky, there were some attempts to utilize it in the past, but they all failed and the pinky is very rarely used, I don't use it at all since it's shorter and weaker, and I can do all I want with other fingers

3. Here are some illustrations I found on the net that may help you

This is a correct posture of a classical guitarist, guitar is firmly in place when placed on the rised left leg, so both hands are free to move
Click to view attachmentThis is right hand from above, notice that thumb and other fingers do not disturb each other
Click to view attachmentAnd this is a front view of right hand
Click to view attachmentHope this helps a bit, I am glad you are interested in this subject, let me know if you need any other help