How should I have played this flop?

[nuclear500]

Fold preflop, you have no idea what UTG is going to do. UTG limpers are always suspect unless you've been playing with the guy and know he's donked his stack up.

But since you called....

Check/fold, you missed the crazy flop of all spades or a straight or top two. Q9 is top pair weak kicker with a huge drawing board, don't let the 9 being higher then 7 other cards fool you, it is a weak kicker.

To the action that did occur? Bet more like half pot on the flop and fold to a raise or check it down if possible.