I'm not sure a raise is the best route to go here. I think these guys have been playing it pretty aggressive the entire hand and you and your opponents have done about everything you could to protect the hands you have. However, they continue to bet no matter what.

SB bet on river shows sign of strength to me. As if he doesn't want it to get checked through or is hoping someone raises his bet. I can't believe he would be hoping to bet a missed flush draw to try to scare the others off (that would seem stupid).
I would guess SB was playing a weak 777 and was scared of T8 Straight.

I'm not sure you gain or lose a lot with either decision raise or call. I don't want to see a 3bet back to me