DOING BUSINESS IN A HUGE POT

[riverboatking]

10-20 NL at commerce. i have ~800, BB has ~1000, MP has ~650.
i have AJ w/ A of spades on the button and MP me and the BB see a flop of J rag rag all spades. spare you all the details of how it got in because its not relevant to the post but basically all the money goes in on the flop (i put the final raise in) so now we have ~2400 in the pot, and the MP asks if we want to do business.
we flip our cards and the BB has 34 spades, the MP has 78 spades and I have the nut flush draw albiet with only 5 outs left.
suprisingly the MP asks me if i want to run it three times. he says either three or one.
basically he was guarenteed 2/3 of the pot and didn't want to lose the whole thing to a five outer.
my question is should i take my longshot chance at winning the whole pot or try and salvage 1/3?