Hand 1, I think you are right, I should have just folded to the 3 bet, as there was almost no card on the turn that would keep me in the pot.
Hand 2, my thinking was I had 9 outs to the flush and 3 more non diamond outs to the gutshot, so although I do think CO would raise my bet, I didnt' want to blast other player out of the pot yet. By check raising, I got 2 bets from each player, so I accomplished what I wanted. I agree, betting may have gotten a weak A to fold there but I thought I had enough outs to not worry too much about that.