in a stud 1-2 game. i have 10 7 - 2 with two spades -- two people call my bring in. Then it's checked around and on 5th opponent bets into me with 8 6 K showing (no suits) -- by this time I've picked up a 4-flush (I've seen one spade in the other hands.) Other opponent folds and it's $2 to me with $3.50 in the pot. I decided to fold since the pot is so small and I'm an underdog to hit my flush anyway.

Is this the right play, or do I have odds to chase my flush here? The way I see it, I'll have to call $4 (one bet now, one on 6th) to win $9.50 (the $3.50 in the pot, plus 3 of my opponent's bets). The odds of making my flush are better than 4:9.5 , so I should chase here, right?

you will hit a flush 45% of the time by the river if you have a live 4 flush on 4th, and your draw was live

He picked it up on 5th, what are the odds for that? Is there any site that has good odds for stud?

i think CP has a stud calulator, I still think he'd have odds to call, his draw is live, he also needs to tell us what other cards he had, cuase he could also have a straight draw with it, he had 10-7 on third, so if he picks up another card to that straight, then he has more outs

CP only has Omaha and HE calculators.
A quick search got me this http://www.twodimes.net/poker/. I've never used it though.