One problem with the fact that I haven't played much O8 (though I have tried now and then) is that I don't yet have a "feel" as far as hand strength that comes from experience...in other words, I know a 5-high flush is generally worth just about shit in omaha, and that a 2nd-nut low draw isn't exactly something to hoot and holler about either...but against just one opponent (who called a steal-raise from the BB), I'm prone to think the flush and the low-draw have a bit more value than in a multiway pot. Correct me if I'm wrong there.
Anyway, my thinking is that on the flop, you have a decent low-draw against one player with the 2-4-5, a flush draw that may or may not be worth anything...and based on your description of the BB, I'd figure there's probably an ace in his hand, so the flop isn't really looking all that great to him.
If he calls me and leads out the turn, I would call down because (1) your flush might be good, maybe he's betting aces up?, and (2) you still have a low draw. But if we check on the flop, then his turn bet doesn't signify as much strength to me, so I'd go ahead and raise.
Anyway, those are my thoughts...I grant you they're probably flawed on at least 18 or 19 levels, but I'm here to learn!
-TW