Even if your moral system solves those "problems", you just "solved" them by substituting the obvious and logical base of utility through personal responsibility. Personal responsibility is no inherent good, unlike utility, if people are unhappy/"feel bad", it doesn't matter how personally responsible everyone is being, that world is still a shit place.

Also, the threat isn't imagined. I can assure you that there are a lot more than one person on earth who would choose to kill as many people as possible if given the option.