Hand 1: Donk flop for 1/2 pot. I shit you not -- scared nits are not going to continue without a hand; AK, AJ and AT could find a fold here.
Once he flats or raises your flop bet, automatically assume TPTK is not good here, and give up. It just cost you like a quarter rather than your whole stack.
Hand 2 was too aggro. You're 5-way, and while statistically you ARE good like 3/4 of the time initially of the time by playing that fast you're narrowing villains' ranges to something that makes a set (or like, Ah2h or 75) a real possibility. I mean, Villain's hand was like one of the worse you could have run into there, and you still had to dodge 13 outs -- you were actually a slight dog. You won THIS TIME, but you allowed Villain to play perfectly; never a good thing.
One very very important thing you have to remember is that non-nut made hands are usually either marginally ahead or behind in massively multiway flops. You can't play them super fast against tight GII ranges to protect your showdown value, because you will just make sure you have none -- one or more people always have SOMETHING and if someone gets it in that something's usually flipping with or better than you.
Hand 3, b/f turn. Pair+FD doesn't have enough
equity on the turn to x/r.