No army would ever want to prosecute a fellow army for murder! Why dig the ground from under your very own wobbly feet?
"War crimes" exist only because nobody wants to call war itself a crime, out of fear of getting prosecuted for waging it. But this is a convention, not a formal concept of law: the fact that murder factually takes place is ignored rather than formally facilitated.
I'll give you your first point, granted but this is just ridiculous speculation with zero screen time evidence to even remotely back it up.
The rationale here is that we know squat about how "forcing out of warp" really works, yet we do know the dramatic motivations of the heroes and the villains, and we have this extremely unlikely ultimate result of the ship being
almost where both Marcus and Kirk might want her, yet still not in the
exact place either would prefer. So we could and IMHO should wiggle the fictional mechanics in order to match the simpler-to-grasp dramatics.
Marcus might want to kill Kirk in view of Earth audiences if he fears Kirk has already managed to send messages to Earth exposing the Admiral's evil plans. It won't do to just kill Kirk off screen then - Marcus has to show Kirk is an evil terrorist who has sent false messages. Staging a play near (but not too near!) Earth where Marcus has all the lines and Kirk acts gagged and bound
might be Marcus' only hope of achieving that.
Kirk has a much better motivation for wanting to be near Earth. He knows he has not managed to send any messages: physically reachign Earth is his only hope of doing so.
So, which one succeeds more and fails less when the ship ends up next to the Moon? I think Kirk does. His motivation is clear, Marcus' is jumbled at best. And if Kirk succeeds, it must be through Marcus' failure to fully control the events.
This then simply becomes an exercise of seeing Kirk in control during the warp chase. Not more in control than Marcus - that is not required. Only in some sort of "not total pushover" sort of control.
And we see that very thing: Marcus fires, and fires a lot, but cannot force the hero ship out of warp until at a location better suited to Kirk's purposes than his. It's not as if Marcus needs to fire just once at a moment of his choosing: he makes a considerable and prolonged effort. And in light of the above, he only "succeeds" after a fashion: Sulu was already at the destination when Marcus' hits produced a decisive result. So perhaps it was a
requirement for that result that Sulu be slowing down? (Say, perhaps fatally damaging a nacelle is very difficult if the nacelle is generating a strong warp field?)
After all, anything else would bring us right back to the "incredible astronomical coincidence" model, and IMHO credibility is preferable.
Timo Saloniemi