[Tha Stunna]

Third is fine.
Fourth is fine, you have a low straight draw against a ton of high hands and there's only one other low draw. Don't raise because you may knock high hands out, and don't fold.
Fifth was bad, you need to raise because you are winning high and probably low. If the J raised third with a 3 flush, that was a very bad play.
Sixth was bad (if you played as I said you would know more by now) because you should raise for the same reasons, although you don't have the low anymore.
River was fine, although if it was just the two of you I might raise, which would probably amount to nothing. No point in exposing yourself to the heart guy if he has a flush.