[detruncate]

If we could guarantee that we'd only have to spend 2 on the turn, I'm calling all day without thinking twice. There's a reasonably good chance that SB will 3-bet in our hand, but we're dealing with an effective 3 bet cap since UTG only has 1 more BB in his stack and BB has done nothing but call, so there's not that much risk all things considered.

Sometimes we're drawing dead to a straight, but both SB and UTG could easily have a wider range -- sets, 2-pair, an overpair, even a strong draw, all of which we're ahead of or drawing live against with close to the proper number of outs at 18+:2 (near worst case of 23:3 if BB drops and it goes 3-bets 3 way).

BB has done nothing but call. He's unlikely to wake up on the turn, and he often has a draw.

The turn is close. I don't think you'd be making a major mistake by folding, but the pot is large and I default to calling when there's any question. Bottom line is that we're occasionally ahead, often have outs when behind (sometimes more than we think), and are never going to have to spend more than 3 bets UI in what is shaping up to be a ginormous pot.