So - you need to put $241 to win $1120 => if he is doing it > 21,5% w/ non-straight-flushes i.e. w/ hands like Khi flush ( Q hi flush at worst) - your call is good.

I think your call is good often enough given pot odds.

Also you should accumulate probabilities he plays combos (6s3s,6s8s) from CO AND he continues OTF with combos (6s3s,6s8s) on FD board with Ace on the board when you potentially hold AA (sometimes suited in spades) or As+:ss type of hand.

detail

when you bet flop and turn, isn't your range more often High( Ace high) Flush than set having in mind you play vs 2 opponents => why would he risk that board pairs and that you c/f river? i.e. why wouldn't he reraise you AI OTT having straight flush?

the last phase of ur comment is another point of the hand (also interesting) he could raise the turn but there was another person (fish) in the pot he wanted  to stay + i might rep some nut flush with A spade wich play i think is much more believable against 2 opponents then against one person. as for your calculations, in this concrete situation i think we should use think processes here much more then math calculations because when i 3 bareel the river with a strong bet i dont think he wold ever value  push k high flush or worst, as for the bluf push i think he is never representing str flush here with blockers because he never allows hemself to make me fold a high flush.

As chance that CO, you and blind all have flushes OTT is not that big, CO can chose either to take all your chips OTT and not win anything from SB (but maybe fish stacks off OTT with set/3pairs, who knows - he is fish after all...), or try to attract SB in the pot by  Only calling turned straight flush. When board pairs OTR, he doesnt get any of your chips when blind leads or c/c. When board does not pair, CO does not get any of SB's chips.

Taking into account stack sizes and possible action after river card, its clear that CO should maximize profit by stacking off OTT. By gaining extra $75 from SB OTT, he only risks to win all your chips if board pairs OTR and then he'll potentially win maximum $75+$290 from SB ( blind stacks off OTR w/ any full)  - which is < of how much he would have won extra only from you by stacking off OTT (extra $440) if his estimation of your ranges/reaction is correct.

But, CO does not need to think so quickly in the middle of hand, for me the speed of his reaction on the turn would also be additional sign what hand I am potentially playing against.

Could  Villain have played this hand by having for instance 3 spades w/  {Ks,6s blocker}\{3s,8s} ?