Hi,
Same old story. Is the nitty guy in MP1 capable of raising less than AQ on the AQ3 2t flop against c-bet after we open-raised UTG, while sandwiched in a 3-way pot?
Flop
Short answer
No, pitch it on the flop.
Long answer
If he's a real nit he has you smoked pretty much always, unless maybe he has combodraws like JdTd, tho you having the Kd blocks some of the combodraws he could have, making it more likely he just has AQ/33. So you're flipping against some combodraws, ~4-outing (some backdoors) against AQ, ~2-outing (backdoors) against 33.
If he's not a real nit, he might raise simple flushdraws sometimes on top of all that, but since he's sandwiched 3-way it's not that likely. Even if in that case, he still has a lot of equity when behind while you're still pretty much dead when he's ahead.
So the overall picture is still pretty bleak for you. Coupled with the fact that we always tend to overestimate how much random tags are bluffing because we instinctively don't like to fold, I'd say it's routine fold full ring barring further reads.
Turn
As played on the turn you don't have a choice, you're still ahead of most of what you needed to put him on on the flop to justify not folding plus you beat AQ, hence you're going broke one way or another.
Hope it helps.