SYG = stand your ground
The continuum of force model might be better recognized as escalation of force principle: a police officer may only select the minimum amount of force necessary to control a situation. As a guideline, in an incident between a police officer and a suspect, if the suspect uses some kind of force to resist control, the officer may only proceed one step higher in the force continuum to achieve control.
I don’t think Zimmerman had any option other than to pull the trigger.
I don’t think there’s a policeman in the world who wouldn’t have done the same.
I doubt there are very few people on the planet who would’ve done anything other than pull the gun and pull the trigger.
Zimmerman doesn’t need stand-your-ground as a defense. There was no place he could go.
The ONLY way Zimmerman could emerge from this having any real culpability at all, as far as I can see, would be if he started the fight.