Emmanuel Derecho

It pretty much means, when you have a set vs a wrap, IF the wrap has a pair on the board for e.g. you have KQT9(wrap) on JT4 against JJxx(set) then the T in the KQT9 is a pair blocker because it takes away 1 potential out for the set to become a fullhouse. Its important because the sets equity against your wrap will decrease by 2% every single pair you have in your hand that connects with the flop.

Snap fold to the cbet?

Answer to your first question is we can bet turn as a bluff. We would want to bet because UTG could easily have 2 pairs and sets in his flop leading range and when he checks turn he is often capped and cannot have many straights. When we bet the turn we allow ourselves to have the very top of our range (which is 58xx and 35xx) and if villain calls turn this opens up barrelling opportunities on non flush and non-paired rivers and often bluff him off any non straight hands.

IF we do decide to take the line above Hero should barrel river almost pot size on river to polarise our range.

I do like your idea to valuebet half pot or even smaller on this river to try and get value from any lower 2 pairs that decided to be sticky on the turn.