I finally (sort of) understand was Fimbulwinter was talking about...

[soah]

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2) He most likely doesn't have a flush

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Why not? If you take his flop lead to be a sign of weakness, then wouldn't a draw be one of his most likely holdings?

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3) I only need him to fold a better hand 50% of the time to make this +EV.

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The reason you have such nice odds here is because your raise was so small, which makes it much more likely to get called. If he bet the flop with a big hand (set), he's not folding. If he bet the flop with a flush draw, he's not folding. If he bet the flop with TPGK and his kicker is a spade, he's not folding. If he bet the flop with TPGK and his kicker isn't a spade, then he still may not be folding considering your image. If he was bluffing the flop but happens to have the ace of spades, he still may not fold. The only way you can get a fold here is if he bet into you twice with garbage.