Your being way too hard on yourself here.
The flat pre could go either way heck almost every decision in this hand could. I personally like it as UTG+2s range is so damn strong here and we're 200bb deep we're going to get paid off well when we hit.
Whether to raise the flop or not could go either way and I feel slagging it off would be hindsight of the flushed turn and UTG+1 waking up. Flatting to keep the other villain in and let overpairs bet themselves in to being commited on the turn. I would side with raising the flop simply because UTG+2 is the villain we think as KK+ and is 200bb deep, stacking them is a priority over maybe getting a bet or two from UTG+1 who is likely just set mining like us, if he hit he won;t fold even to this raise.
The turn raise is fine, we can;t just flat such a tiny bet with so few combos of flush out there and have QsQ+ draw out on us for free.
The river we are probably ****ed but we've got lol odds
, weaker sets sjould get us through the JJ/AsKs/AsQs hands that we will see most the time.