AJ vs 3bet

I'd play it thesame way. With just 3 players on table, and having position I would also just call his preflop raise. Flop is easy call. Turn is a bit more expensive, but in position I'd still call. River I fold unless I have a read.

I think that somewhere along the line -- probably the flop -- you need to raise.
Make villain be the defender. If you raise you can fold to a shove, which will be ultimately be cheaper than calling then turn bet.

I could be wrong -- but if I am, then what range does he have that 3Bets pre, that AJo beats on that flop?
Since you don't raise, he could easily think his KK or QQ is ahead and push you off your Ax

Also, you could establish your authority by 4Betting pre-flop -- AJo is on the edge of 4-Bet/Fold though.

Curious to see what others think

You could 4bet pre sometimes, but bare in mind that people under 3bet rom the BB.
Against a top player this is a call down on this runout. You can't raise because he has AA, AK, AQ and you don't.
Raise your A8, A4, A2 etc. AJ is a call down.
At NL10, don't ever call this down without some solid info.