When responding to aggression, the response should not significantly escalate the risk. So lethal force should only be applied in scenarios where there is a lethal threat, etc.
You're not required to risk your life for someone that's victimizing you. You didn't create the situation and your responsibility is to defend yourself and your loved ones.
No, that's the lie cops use after the fact to hide their crimes. Just because they're trained to use certain words to murder it doesn't mean the concept is inherently corrupt.
I've been caught in a bomb scare, guns would have done fuck all when there was a massive police presence that the trains were stopped and the shut down a whole part of a city. In fact a gun would have made me more likely to be killed than going the fuck home.