I think another informative thought exercise is to consider what the police would have determined if they arrived on scene to find that both George and Trayvon had died. Trayvon from the gunshot, and George from a sudden aneurysm immediately after firing said gunshot (just as an example of how he could've died right at that moment.)
So, cops show up and they find these two people laying on the grass... what would they decide happened based only on what they could glean without benefit of Zimmerman's statements?
Well, they'd see that George had all the injuries, apart from the near-knuckle abrasion on TM and the gunshot of course...
They'd quickly figure out that George was the one who'd called their non emergency number shortly before, and they'd figure out that this must be the guy he described, since he fit the description, clothing, etc.
They'd talk to Witness 6, Witness 11, etc and piece together what happened...
and I think it would be very clear to them that it was a self-defense shooting.
So yea, I think it's helpful to consider angles like this, which eliminate any considerations about George's supposed "lies" and just boil it down purely to the other evidence.