I disagree with you on one point. It appears to me the camera must have been about the level of the girl’s chin.
Perhaps, but I don't think you would see the top of the girl's head so clearly if the camera were level with the girl's chin. Also, you are looking almost level with Martin's chin and yet he does not appear to be tilting his head down. If the camera were level with the girl's chin you would see under Martin's chin unless he had his head tilted forward rather drastically.
Just my opinion.
If you're correct, then it's an even greater argument that Trayvon is not over 6'0" tall, because it increases the angle from the camera's point of view to the top of the door behind Martin.