Hand 1: I'd have checked the flop, made a pot size bet on the turn (if it was still checked around) and called about a 1/3-1/2 pot size bet on the river.

Hand 2: Check the flop if anyone makes a decent bet (1/2 pot+) I ditch the hand. Make a decent bet on the turn and likely check down the river. (if possible, fold to a decent bet).

Hand 3: If you have a set it's about 1-2% that your opponent has a set too. So you never worry about it. I'd have pushed on his reraise. Doesn't really matter though since you were going to get all your chips in the middle and lose.

Bear in mind that, with the exception of HH#3 you had big pots with one pair. That's not a big pot hand. You should try and keep the pot more manageble without 2pair+ especially at the low levels. If your heads up you can get more aggressive with TPTK.

GL.