Drawing Hands and Pot Odds

[redraw]

I have some confusion over playing draws as it relates to pot odds. Specically in limit HE I find it seldom correct to fold an open end straight draw on the flop, but frequently correct to fold it on the turn...yet my flop call justifcation assumed playing until the RIVER... Does this seem contradictory to people?

For example: $5/10 HE, and our hero is in the BB with 9To. One MP limper, SB calls, and hero knocks the table.

Flop comes K 7 8 rainbow

Hero assumes he has 8 outs to win the hand (count 0 partial outs for a 9 or T). SB bets $5. Pot is now $20, thus offering the hero 4 to 1. Because he is 2.18 against to make his 8-outter by the river, he calls. MP calls as well bringing the pot to $30.

Turn brings a 3. no possible flush draw. Board is K 7 8 3

SB bets $10, so hero is now getting 4 to 1 pot odds, but he is 10.50 to 1 against at this point, so he must...FOLD?

My hang-up is that hero justified the flop call by using 2.18 to 1 (31%) as his hit rate- this is the likelihood of completing the flush with TWO CARDS to come. But when SB makes the prohibitively large $10 turn bet, the hero must fold- so hero did NOT really have two cards to come...only one (the turn, on which he missed)

Am I thinking about this the right way? Thanks for any responses...