I'm aware of your theory and I think it's doable to check it out. There is documentation everywhere-- we just have to find it.
Also, I have fired up the printer to read your finds closely. I'd like to get a look at the references, too.
You're right about the oft-repeated replacement of Iodine with bromate. I tried researching the flour industries and what they call food "fortificants" -- and found that bromate was probably the least toxic thing added to flour. There are so many other pesticides, fungicides, anti-rodent chemicals, anti-caking chemicals,you can gag just reading it.
But I found a hard cover book published in the 70s in which doctors complain they could not get their new radiation equipment to work because people got so much Iodine in bread that the radioactive Iodine dye couldn't get good pictures. The dye will only "land" if a person is iodine deficient.
Seriously, grad students getting a Masters of Public Health would find this a great research project. We need to recruit them. We've invested so much of the last years finding clues that now we need a full timer to run with our spade work.
There is still a multi-leveled mystery here. I can't invest the time I would like but like you, I would be happy to brief a student on our independent scholarship. Your questions must be addressed.