But my personal opinion is to wait for the anime adaptation, which is not going to take too long since season 3 is being aired from the next week itself, and it will take only around 2-3 months for the scene to actually get adapted.
But it depends on what way they adapt it. If they show a full POV including both Kisaki and Izana, then they can give way to the second and the third possibilities, but only when they show Kisaki firing the first bullet and Izana then pushing Kakucho, or if everything goes well, they can even show Izana running as well. Plus, they can actually even give the idea of how much distance had Kakucho actually run as well (in this, I mean the distance traveled by projectile gets lesser, which is bound to happen lol).
But let's say they take both POVs differently, then even Dalesean's assumptions wouldn't fully make sense (even though Dalesean gave the best lowball possible for the feat) and this feat would be around the level of normal humans
.