So...he is just supposed to follow the story and let himself be killed? Just because they were supposed to have happy lives, is he supposed to just sit there and happily die for the sake of their success and happiness? Why? That makes no sense. Also, why is it wrong to use whatever advantage you have to succeed? That's ridiculous. Is a person who is born a genius a cheat because they have an unfair advantage when competing against and average joe in a test of wit?
Also, him trying to stay alive is already him breaking the scenario, since his death was part of it to begin with. The whole "I gotta keep the scenario from breaking" is a a stupid plot point in ANY story in which the MC plays the role of a person that's supposed to die. Unless they are willing to sacrifice themselves for the sake of the story, there is no way to keep the scenario from breaking. The difference here is that he is not going to naively believe he can keep the story from derailing, and is now actively using all of his strength to its fullest without the need to hold back, consequences be dammed.