PREFLOP: This is a must raise! You have a strong equity edge in this situation, you must raise to exploit this edge. Just calling here was a grave sin.

FLOP: If I read your post right, there are 7 people seeing this flop including you and the BB. In this situation I like checking better than betting, since someone is very likely to bet and you can then checkraise for elimination or checkraise for value depending on the action. In your situation you couldve accomplished both objectives, by checkraising you couldve forced the live one to either fold correctly or call incorrectly and you couldve got more money in the pot by making the solid player and the NG put another small bet in. Checking and calling in this situation was again the wrong move in my opinion, you shouldve raised.

TURN: There is 5.5BB in this pot now, this means that if you bet, no one will be getting the correct odds to call with a gutshot or even a 5 outer, since a bet will protect your hand there is no reason to go for a check raise now, plus if you bet out the solid player may raise to protect your hand anyways, another problem with going for the turn checkraise is that there is a chance that this turn may get checked around and 3 opponents seeing the river for free would be a catastrope for your one pair hand. If the flop bettor was directly on your right checkraising the turn would have more merit, but he is not so betting out the turn for reasons I have listed is the better play IMO.

Given the way you played the hand once the NG bets you must raise and you did so I like your play there. Once the NG 3 bets you are in big trouble since his most likely hand given his play thus far is 55 or 33, it is also possible he has J8s but he probably wouldve raised the flop, or he could have 53s but he probably would not 3 bet the turn. You have a profitable draw to beat these 2 unlikely hands and theres always the chance your opponent is overplaying AJ or he has some BS hand like Ah5h. Since the pot is now quite large(10.5BB) and you are against an unknown I think you should call down.