[spy587]

Hand 1- I fold the turn.
Hand 2- If he really is a huge fish, this is all read dependant. Would he do it with nothing? top pair?
Hand 3- I check the turn and call the river if I miss.
Hand 4- In this case, I call the flop and c/r the turn. Then I lead the river. To me it looks like CO prolly has nothing, but this is also read dependant.

In Limit HE the PT stats are very important.

Edit: Looking back, HAnd 4 3bet is far better. Need to find out where you are.