I'd bet pot on the flop, be happy with a fold, and if reraised all in I'd call.

The worst situation you can imagine, you are 30% to make a full house and bust him. It is absolutely IMPOSSIBLE to put a dude on an ace high flush headsup in a tourney situation.

Actually the play you made wasn't bad if the opponent is very aggressive. Otherwise it's very wrong, because you won't get a high spade out in this situation by a pot bet of the flop.