1 & 2 - two pair against a set usually you should go broke, TPTK sometimes you do need to re evaulate if someone is calling every street - if there are draws out it's less scary, but if the board is nasty like you menion, what hands could dude be calling your bets with? You're down to reads here, will this guy call with second pair or TPGK? What is your table image, have you shown some weak hands? If you've been playing tight and another tight player is calling you down, TPTK is usually no good.

In the first hand you mention, you may not have had a read before this hand, but you sure do now, this is a guy you need to play any reasonable hand against. Specific to this hand he got very lucky.

On the last hand why are you betting once the second A comes - what do you think he called you with on the flop? It's bad luck but this is now a pretty easy fold. No way your hand is good there. Why would he raise with the nut full (or quads as it turned out) - giving free cards is good here. Seems like you thought the second A was a good card, but I'm not sure why.

PS if you bet the river and he didn't raise, he's the worst player ever.