Don't worry, you didn't say anything wrong and your post was very informative.
I think the comment was related to the sheer number of issues that you said needed to be considered -- sounded very much like someone who had "just been there", had learned a *lot* in the process, and was still a bit bruised
EDIT -- Tom, I second everything mdrew said. Given your seating height and screen height, the bottom of your screen should probably be 23-24" off the ground. That would put the "1/3 of the way up the screen from the bottom" point at eye level.
SECOND EDIT -- Make that "I second everything except stretching a 4:3 image to 16:9 and watching it that way".
I *hate* watching stretched images
