I'm trying to put myself in the opponent's place. Limp 5 handed with an 8-7 of spades? J-10? UTG?

Well, it's possible. Call $5 more to me? How drunk/frustrated am I?

On the other hand this makes more sense if I hold a pair. What the hell; you could have A-K or A-garbage

Now on the flop, when you raise $12 and I go over the top and double your raise, I've either put you on a bluff (unlikely) am drawing to a flush and feeling very lucky or--most likely I've either

a. Hit a set on the flop.

b. Think my pair of 10's J's Q's or K's has you beat with that ragged flop

So either go all-in or fold after 'my' reraise on the flop. The pot's big enough, can't see continuing to call, even if you think I'm a maniac on a nutty draw or bluff--and you haven't indicated any sort of read, just the pain of getting a scare card on the turn.

So, I repeat that the correct play was to fold or go all-in.

Which one?---- Beats the hell out of me

I don't think it's an easy fold