Pugsy hit the nail on the head when he said "To get metal to be the proper shape, the metal needs to be thinned or thickened pretty much an exact amount everywhere on the panel.". Your metal thickness is simply skewed too greatly and the original shape is long gone. But...
Again I see progress. Again however, we can't touch it. The difficulty level is too high for the individual at this time. Now its a mess that ought not to be hung on a car. Has been for a few pages. I am cynical by default but tried my best to be optimistic because the enthusiasm is so there. I support your suspicions about the method of application of heat being where it went wrong.
Stick a new roof on there and try not to let this experience negatively affect your thought process as you move forward on the project. There was a time when you needed about a cup of filler on that roof skin. At this point, even if a metal miracle were to occur, you'd still have bondo over the whole roof. That is the best lesson you can take from this, in my opinion.