“In what way does the screen stuff not support X ?”
I was using it as a general comment on how to interpret the information provided in the movie: do you go with what a character says is going on or do you base your decisions on what is shown on screen?
Both, and I think it's enough to have a good idea of the plan.
Marcus wanted to eliminate Khan with the torpedoes. An ironic way of killing his own crew, as well. The torpedoes would spread and damage locations around Kronos, prompting the Klingons to find the disabled Enterprise and destroy her, and leading to a war that Marcus thought he would win with either one or several Dreadnaughts.
tlrd for me (too long, read diagonally).