I agree with you...later he is in retreat and Trayvon calls out to him. But initially he is still giving the following impression to Trayvon.
So there is a mistake by GZ followed by a mistake by Trayvon...although no one is doing anything illegal...GZ gives the impression of still following and Trayvon gives the impression of "oh S---" to GZ.
And this is where your vacillation falls flat IMO.
Zimmerman isn't following Martin...in his mind, he's good.
"Ho dee doe, I'll just head over here and get an address for the police, I've done my civic duty, the neighborhood is a little safer, if I didn't scare that guy off the police will."
Maybe he waits over there for the call from the police...I don't know...they kinda gloss over that in the walkthrough.
He doesn't get a call, says to himself "I'm bored, going to head over to the mailboxes."
Hum dee dum, across the dogwalk, to the T...and there's Martin!
Freeze everything!
Murder and manslaughter are predicated on intent.
If we agree up to this point, Zimmerman has zero intent.
Involuntary manslaughter is predicated on negligence.
Is it negligent to get out of your truck?
No.
Is it negligent to follow for the purpose of observing the activities of a suspicious person?
No.
Is it negligent to STOP following a person and go get an address for the police?
No.
Is it negligent to walk across a concrete sidewalk to meet a police car?
No.