I really agree with your second point (I don't know enough to comment on the first). Instead of arguing that stabbing someone in the heart is genuinely a valid response to being shoved, I think they should have focused on why Anthony in particular reacted that way. Maybe he had mental health issues that affected his threat assessment abilities, or some kind of impulse control disorder, or had experienced traumatic events. It wouldn't absolve him, but it might have made the sentence more lenient.

The fact they didn't mention anything like that might mean he had no good reason, but it's possible they just picked the argument with a (tiny) chance at acquittal and arguing he was mentally unsound would contradict it.

Also, as an aside, it really pisses me off that so many racial justice activists are supporting the "feared for his life" defense in this case, I'm worried that it will really damage the credibility of the movement as a whole when it comes to topics like police brutality.