id fold the river and be pretty happy about it, there's just so many more arguments for folding the river than calling IMO. i think every other decision is 100% standard.
1) all the spade draws are there for justin 200bb deep in position, and bb sitting out
2) you can have all the spade draws as well, raising the turn with any hand is pretty spewy, and in turn he bet the pot so you cant really fold anything like AxQs or QsTs which is what ur repping. so air-bluffing in justins spot is pretty heroic since you can definitely have all the big flushes.
3) There aren't many pure air combinations on the river for Justin, especially when hero has the A
4) He knows you're capable of knowing his range could be polarized and thus capable of herocalling with 1 pair just as often as a small flush
5) Justin probably thinks given all the factors like BB sitting out + first hand of 25k could level you into herocalling more than herofolding, hence the overbet.
I think point 3 is the biggest factor