Same Example (correct me if im wrong)

Pot is $3. Villain bets 2/3 pot which is $2. If hero calls the final pot will be $7

Made up of the $3 pot + $2 bet + $2 call = $7

Hero contributes $2 out of $7 (do we discount previous betting rounds because that money is no longer ours and belongs to the pot?)

So hero needs to win 2/7 showdowns to breakeven or win 29% of the time. Therefore if villain is bluffing more than 29% of the time calling is +EV?

Can we work out how much EV we stand to gain from this if we know a villain is bluffing on the river 40% of the time for example? (I'm aware we can never actually know this but just as an example)

So we should just call with a selection of our stronger hands with good showdown value vs a LAGGY villains range when we need to win 2/7 to breakeven as villain could be bluffing with the best hand on some occasions and calling too frequently would be -EV?