Surfing Waves

Please give me some rules as to how far apart your legs should be, I noticed that the shorter the board the farther your back leg is from the front. Also, some tips on pumping when legs are so far apart as well as on weight shifting depending on the position on the wave and what you are trying to accomplish!
Thanks!

One thing surfing isn't about is formulas or rules on how to do it. So even though I understand your thoughts my answer is a little different from what you would want.
Foot positioning is a changing field, too wide apart ( poo stance) and you cannot give weight changes to direct the board too close together ( ballerina stance) and you have a very limited centre of gravity and again hard to change board direction.
I advocate ballerina poo!
Short board surfing is designed to give all the movement and drive from a base position with the back leg over the fins and the front foot in a comfortable position forward. Weight changes between the back and front foot adds drive or stalls the board then pressure on the rails with a slight movement and back foot pressure initiates the turn.
REALLY though the only way is not through theory but by getting out and surf surf surf, each little success adding to your skill set. Pumping is stringing together little turns each one adding a little more speed to your flow along the wave, sort of like tic tac moves on a skate board.

Is the Avatar picture of you?
Post some pictures if it is fair comment can come from those too

Only rule if it works it is OK

As on old man who used to surf when he was younger I can tell you my stance has changed. The wider the stance (up to a point that being where the stance is so wide you have trouble keeping your balance) the lower your center of gravity and the more resistance to falling off the board. The problem I have as an old man is when I try to crouch in a wide stance say like I am wanting an even lower center of gravity for a turn or I am trying to fit into a small tube I find that I can't do it and end up pulling a groin or something. I used to be much more flexible. So my suggestion is to find a stance that allows you to change to a crouch without hurting yourself to start off with. After that you may have a few more stances to use in other situations.