Broader? I already was
Ok, point taken.
I did not believe it played a key part. Probably to the development of the war and to explain what Khan was but not: Genetic altering = Mentally insane totalitarian will be born
I think the idea given is that superior ability produces superior ambition. He wasn't arrogant just because, he was arrogant because it was a natural product of the tampering with his mind.
From the main cast, not from one episode villains.
I think if the villain was memorable enough it can work.
Spock arrived too late to save Romulus. That in itself is failing to go by his word and save the planet. Nero thought he would save his planet and Spock failed to do so. Spock was, then, indirectly responsible for Romulus from Nero's perception.
Spock had no obligation to Romulus or its safety. He didn't put them in harm's way. Kirk having obligation to Khan is debatable (personally, I think if the Federation exiles somebody dangerous, they should probably keep tabs on them). He technically did put them in harm's way.
I believe Khan being stranded was kept off of the records, wasn't it?
So because they were, why would Starfleet be involved? Starfleet did not even know of their existence.
I don't know. It doesn't really make sense to not have any record of something of such importance. Just because they dropped charges doesn't mean they erased all their logs and never reported it to Starfleet.
That he agreed to
He agreed to somewhat difficult conditions, not dire conditions.
He was pissed off for 25 years, that isn't short.
He endured one event that he had the potential to change. With that opportunity, that he sulked for 25 years isn't the fault of anybody but himself. If Khan were given the choice to change how things went, I don't think he would act the same. That's the big difference with time travel.