What should be the average stack size, if you want to call a preflop raise, with a pocket pair for set value, against 2 or more players ?

Or has anyone an idea, how to calculate the Average amount of win when you hit your hand, depending on the number of players ?

I think this excerpt from Hoke's first footnote begins to answer these questions:

IMO:

The article is obviously correct in it's overall theme and the presented math helps to illustrate a point, but the idea isn't that you can come up with a formula that tells you when to play a small PP.

This wasn't the first time I've seen the stack size argument presented and I still think it's much ado about nothing. It's clearly true that when the stacks are smaller in relation to the blinds they will also be smaller in relation to any bets or raises and any implied odds calculations should therefore be relative to the stack sizes of the participants.

But I don't make any decisions based on the stack sizes themselves -- I make a decision based on the implied odds, which are relative to them.

I also think it's often easier for a shorter stack to become pot committed, so implied odds actually approach "stack odds" as your opponent's chips begin to dwindle.

Finally, other callers in front of you is never a bad thing. Some of the money you need to justify your call is already in the pot and when you hit, you have a better chance of extracting a little value. Besides, unless you're in the blinds, you'll have a positional advantage.