I can't do much more to explain it. Read the ToP (or maybe it's in SSH) section on it. You don't raise for a free showdown to fold out a better hand. That's called a bluff-raise. You raise for the 3 reasons I mentioned before.

You say you don't want to fold out a worse hand on the turn with a raise, but then you turn around and say you'd raise the river if you hit, but why wouldn't he just fold the river to you raise? And what makes you think he's going to fire yet another barrel at the river with a worse hand, especially when the board gets scary? Or even call you're bet if he doesn't fire?