The operable word being “reasonable”.
It was reasonable for Zimmerman to believe that someone sitting on his chest pounding his head into the concrete was actually a threat to his life. And the purpose of the one shot was to “neutralize the threat” — not to kill.
In this case is it reasonable to believe that a kid carrying a pellet gun walking away from you is a threat to your life???
Is it unreasonable to believe that if the kid hears something behind him that he shouldn’t turn around to see what it is or who it is???
Is it reasonable to believe that a kid with a plastic pellet gun is then as he turns around going to raise it up to shoot somebody with his toy???
Is it reasonable to believe that the deputy said anything to the kid or gave him any time to respond if all of that along with 8 shots happened within 6 seconds??
Is it reasonable to believe that it took 8 shots to neutralize a boy with a pellet gun turning around to see what the commotion is???
Yep — REASONABLE is the operative word to describe what the deputy lacked.
Yes, since it's not reasonable to expect anyone to know it wasn't a real gun.
The rest of your questions are non-sequitur sophistry.