[JohnG]

Difficult to say without knowing anything about your opponent, and what his preflop raise and post flop play could mean- although the number of people that saw the flop negates this a little. He probably was either slowplaying the flop or just picked up a flush draw on the turn (maybe 6c8c if his min preflop raise could be hands like this). Given the description of your image and the texture of the flop, he could easily be checking as little as top pair, expecting you to bet.

In general, I would fold when he moves allin here, as it is difficult to see him calling the flop with a hand that just picked up a draw and you have also shown strength in this situation yet he still moves in (not a good spot for him to semi bluff normally, but is a good spot to put you on a king and expect his allin to be called). I just think you are beat more often here than you will be ahead.

With your style and image:

I probably still fold preflop.

Checking looks a reasonable option on the flop, given nature of my hand and the texture of the board.

If for some reason I had bet the flop, I would just call his turn bet, with the intention of calling a small riv bet if flush misses, but folding to a bigger bet. And folding to any reasonable bet if the flush hits.