That is so rough, I feel for you. Spending that kind of money and getting a worse result than the cheap pan would drive me up the wall. Honestly those heavy dark coated pans can run hot on the bottom, which explains the burnt edges before the middle sets, so it might not be you at all. I have had the same thing happen and went right back to my beat up old pan plus parchment. Does the pan feel really dark and heavy compared to your cheap one? That is usually the giveaway.

That zoning thing from 2008 is what gets me. If the towers were placed around the same time the property rules changed, then somebody knew way ahead of time which spots would and wouldn't have signal. Dead zones don't just happen by accident most of the time, they usually mean nobody paid to put a tower there, and there's always a reason nobody paid. You should pull the tower owner names too, not just the locations, because who owns them tells you a lot more than where they sit. Curious what came up when you looked at who filed those zoning requests back then.