AQs is a monster in any position. Checking back PF is really, really bad. From the BB, PF is the only street where you will assuredly have great position to value bet this monster. So do it. If you flop big, you are going to kick yourself for playing it so soft.
You have to lead this flop because you don't want to let the 2
draw for free. And this board is going to freeze up most of your opponents. Unless they've got broadway or the flush.
B/f is the right call on the turn. At least when CO raises into the BTN.