Another way to think about this spot is that it's largely about how often we have QJ. Prahlad's river jam has to work ~60% of the time if he's bluffing for us to be losing to him bluffing too much, and if we have 16 combos of QJ here (is there a word for in our eyes? In his eyes we can have 12 or 9 depending on his own hand) his equity with a bluff changes massively depending on if his hand is 87s or J9s.
Our combos of QJ inform what his bluffing range should look like. It's unclear what his turn range is, but his bluffing range should include something like J9, Q9.
Bluffing ranges should include defense against blocker calls. It's actually possible for Prahlad to balance his range so that calling with KQ and AK have the same equity, and if we are going to call perfectly it makes sense for him to do it. Basically we can start his range at QJ, then add in bluff combos making sure that no bluffcatcher crosses zero equity before the others. If KQ has the most equity as a bluffcatcher we should add AJ to our bluffing range to lessen its equity, and if after doing that AK has the most equity we should shift the proportion slightly more towards hands which compensate back. Basically to have a perfectly unexploitable shoving range we should construct a range for which every bluffcatcher has a zero EV call, which is perfectly doable.
A way to think about this at the tables is not as "merging" but as "tripolarizing", perhaps. We have three range segments - air, nuts, and hands which are good against his best bluff-catchers by nature of their showdown value and blockers.
While balancing this range Prahlad has to always seek to have blockers to QJ with his bluffs. If we call perfectly he wants to strive to give us 0 EV calls with everything while minimizing the EV of a call with QJ. If he can take a call with KJ from -20 EV to 0 EV he can snag a bit more of the pot, but if that changes the QJ call EV by greater than 20 in our favor it's a losing play for him. Our QJs are massively massively important.
His betsize needs to account for how often we have QJ. For this to be a correct betsize we need to have QJ less than 8% of the time; if we have QJ more often than that it becomes better to bet a balanced range at a progressively smaller betsize. The reason is that increasing his betsize increases the ratio of nuts:air that he can have to bluff us off KQ or AK. If we have QJ more than 8% of the time making a 2x pot bet instead of a 1.8x pot bet loses more money by getting bluffs called by QJ than it makes money by allowing more bluffs to fold AK/KQ. I work through the exact equation for determining this at ppv.gainmes.com.
Whether or not to call with AK is just an information gathering exercise. Does he bluff enough or not? I think these days it's reasonable, with technology, to answer that question with AK against most opponents. Against some it's going to be a massively +EV call, against some it's going to be massively -EV. If you can't work out whether it's +/- EV then it doesn't really matter, just call 40% of the time I guess, or 100% if you want that image, or 0% if you don't want to show your hand.
Against Prahlad in this hand if we start with the assumption that he donks turn with a reasonably balanced range the main factors are
1) does he valuebet worse than QJ?
2) does he have J9, Q9, and follow through?
3) does he turn AJ/AQ into bluffs?
My guess is that most of the assumptions give this as a fold. Note though that if he is valuebetting worse than QJ with this betsize he's making a massive mistake and you're going to print money with your combos of QJ, so whatever.
It's sort of fun to talk about whether AK is higher or lower than 0 EV to call with here, but irritating that people still just say "higher" or "lower", instead of what they think it is. My guess would be that a call here is very bad, maybe -$2,000 on a $10,000 call. It's useful, in my opinion, to give a numeric value to equity of the decision when making a choice, as it's the clearest way to voice exactly how close you think the decision is. Also once we become more using to talking about decisions in terms of EV we can start having equally interesting discussions about whether to raise or call on the turn (I'm shocked that raising turn was just immediately thrown out of the question), or what the EV is of a turn call with QJ for us.