Against a player who seems to be shaping up to be a bit weaker having limped the BU, this is an easy raise preflop with AJ, particularly since they have lots of lovely chips waiting for me!
At the very least you take your opponent out of their comfort zone. By playing the way you did you let them dictate how the hand will develop and especially with them having position on you, it's difficult to know where you stand, therefore, as you so rightly point out you then end up folding which, I might add, is leagues better than most people can do already.

I'd suggest trying to be more aggressive and take the initiative away from these guys when you have a good hand; make it uncomfortable for them to play their game and see the diffierence it makes to your own game to.

As an aside I'd fold to, that river bet from your opponent is just way to big.

Gl.

Should always be raise pre, just wanna get value with your big hand against weak players.

River, I think is tough but depends on dynamics. Has this guy been a loony often? If so I make a hero call, but I think you make this easier by raising pre and there being more money in by the river.

Big mistake not raising pre flop. We have a clear value hand, and should be crushing a limper's range. Initiative is also important when hoping to maximise value.

I would suggest that you check out the video section of PokerVIP and watch some live play clips. Pay attention mainly to pre flop and sort out that part of your game first. Mistakes preflop can lead to even more expensive mistakes later on in the hand when the pot gets bigger.