Hand 1: very annoying.. I might be tempted to just push the flop here if I had been playing aggressively at that time. And I call the river as played. The 3 didn't help him so why call the turn and fold the river?..

Hand 2: I fold the flop quickly. If you call I think you have to see it through like you did.

Hand 3: I bet the flop here because there are 4 other people in the pot. If you slowplay then the rest looks fine. Slowplaying the flop isn't that bad here imo because the pot is already juicy compared to stack sizes.

One more thing.. your check/raises can be bigger. Remember that if you raise to the size of the pot over a bet, they have to pay less than the pot to call.