Flop is fine :
SB range on c/r will consist in 66/AQ/bluffs. Some opponents love to 3b mid pairs here "to find where they're at", but it's still a bluff (with decent equity actually). 3b would only achieve to have him fold hands you beat, and call you with hand you are crushed by.
As for his bluffs, usually you want to bluff your best folding hands, with some backdoor equity, so mid/bottom pairs, Ax (AcXc being the best) and maybe KsXs (KJs/KTs) and JsTs
And with BB cold calling the c/r, I would be a bit worried of Q6s/66s trapping, even though he mostly has Qx there.
That's why I think calling is best
Turn is I think not optimal:
- SB checks and BB checks.
First of all you can eliminate BB of the equation as I don't see him keeping this passive line with any hand that beats you. Sure he could have a flush, but no decent opponent would flat the flop with a flush draw (and not even the nut flush)
When SB checks, this should raise questions :
- Lot of people are more likely to c/r the flop with the nut flush draw, than a Ks/Js (although I don't think it's a good line). But even if he c/r a flush draw, he would always bet there to get value from Qx and protect his hand. So really this flush shouldn't be a worry.
- His value hands (fullhouses) would bet for value there almost always, especially with the flush now. If he checks he knows it's most likely going to be checked around.
- His bluffs should check and give up a fair amount. Typically you'd want to continue some bluffs that got backdoor equity on this turn, but on this board, this pot and multiway, it's reasonable to abort a lot of bluffs.
Hence I think betting the turn is optimal, probably on the bigger side, because of the 3 spades. It would be pretty bad to check against BB holding QJs for example not to mention KsQ. A case could be made to jam.
On the river BB has almost always a Q here, meaning SB can't have a Q, which is a important info. All together, that means he has 66 turned into a bluff (very unlikely) or a random flop bluff.
Now a lot of flop bluffs have an A in them, best ones being AcXc although that's pretty negligeable on that flop.
Finally, he bets 5k into 14k, which I don't think he could ever get away as a bluff considering the action: a Q isn't likely to fold for this amount, and it's pretty likely BB or you has Qx.
You need to pay 5k to get 24k, even if actually it's 12k since you'd always chop with BB. So you need to beat SB 30% of the time.
As played I would call only if I perceive SB to be somehat spewy or not knowing what he's doing. I have no idea about the field level in this event, but if my opponent is decent, I don't think I win enough of the time.
That said, in most random online tournaments I'd call and complain about how unlucky I got