(2) How does Trayvon know Zimmerman is "leaving'? From his perspective maybe the guy simply changed course and is continuing the search?
You and I can speculate that Zimmerman is telling the 911 dispatcher the truth about his intentions ~ but that's only because we have access to the recording.
Maybe Zimmerman should have shouted to his quarry that he was leaving now, or maybe he could have taken the opportunity to announce that this was private property, it was posted, he was Neighborhood Watch, and unless you had a legal reason to be there, to leave the premises.
Something like that.
We identify our Neighborhood Watch folks. Apparently that development didn't.
But that's all speculation. You had a young man trying to get "home' in the development on a "Dark and stormy night......" He had a fellow in an SUV following him.
This was probably not the time to start a manhunt
Normally leaving is not a matter of quibbles — and neither is approaching. I clearly see you are entering into quibble mode.