1. A loose aggressive will raise you if he feels ahead. Calling is VERY weak and "chasy"

2. Firing the third barrell with a weak hand, and little chance of it being called by a losing hand is not optimal against any opponent who will bluff a lot, or a calling station.

3. If you feel you have the best hand against an aggressive opponent, then checking the river and snapping off his bluff attempt is often the correct play.

Firing the third barrell with a weak hand should generally be reserved for hands you play with tight players who hate to pay the pot when behind. The purpose of the third barrell against a tight player is to get them to fold. This is incorrect a lot against an loose aggressive player (see 3) or a calling station (loose passive) type player.