Most Annoying hand in Vegas

After coming back from vegas there is one hand i keep pondering...

I have a LAG image. ONe guy actually tells me that he doesn't think I can have it that often.

Truth is i was on a rush of card and i didn't have it THAT often, but often enough to be sitting with about $600 on $200 buyin.

Table is loose passive. I'm 3 from button, and entire tables limps to me. I look down at 99 and raise 10xBB. Shockingly, button guy who was one who told me two hands ago that he doesn't think i have it all the time, calls. Shockingly, the rest of the entire table calls. So thats $20 x 7 = $140 in pot. flop comes 5s6s7s. I have 99 w/o the spade. checks to me. I decide to bet $60. Button guy reraises instantly to $200 for $140 more. It folds around to me and I think about what he can have. I eliminate possibility of him flopping nut flush because I think it'd make more sense to trap here. But the fact that he instantly raised me w/ absolute confidence makes it a possibility right? Online, I would have read him as weak. In person, I thought strong. Then I ask a nifty question, "Will you show me at least if I fold?" He says "sure" Anyway, I think for like 5 min. management is tired of it and time me. I start thinking I have him beat and he's on a flush draw, but I can't be sure. Even if he's on flush draw I'm only 2:1 favorite, but if he also has two overs.. I'm not even that. I know he doesn't have an overpair because I seen him ALWAYS reraise preflop MINIMUM w/ that kind of hand. Thinking back, I think is likely he overvalued his 97 w/ the 9 of spade since when I folded, he showed me the 9s then claimed he had the nut str8 flush. I instantly laughed and said that I didn't believe him. I said that if he had the nut str8 flush he'd show the 8s9s both proudly, not just show one 9s and then muck the other one. If he had 9s7d or something, then he had 3 outs from the 7s, and 9 outs from the spades for a grand total of 12 outs. That means I wasn't a strong favorite and would essentially be gambling. At the same time, it also means I folded the best hand in a plus EV situation. What should I have done?