Welcome to the AZ rust club
I also recently purchased a supossedly rust free "AZ car"....only to find out that there was a significant layer of bondo on the car. Same rust areas as yours. I'm almost convinced that a truly rust free GT (AZ or otherwise) is a myth. Sorry to get on my high horse, but now I have 2 rusted GT's! I suppose you have to decide, as I do, based on how much money you've invested at this point, is it worth the added expense and effort to do all that patch work. Can you do it yourself? If not, it will cost you a fair amount to get the work done unless you've got a good friend in the business. You'll also need to make sure that no structural members are rusted. Once that happens, it becomes more than just a patch job.
Now I've never welded a piece of metal in my life, but from what I have heard from this and other groups is that the metal on the GT is pretty thin...but it is still weldable. It's not necessarily the welding that is the issue, it may be forming the pieces to fit. If you intend to do it, you'll need some sort of small press brake and quite a few other pieces of equipment. Anyway, I guess I'll stop babbling now. Obviously I'm pretty dissapointed in my own situation, but maybe some of my rambling can help you with your own GT.
Best of luck, Jason