I'm a dabbler.
It sounds like you guys have been through hell. I'm sorry it's been so ruff on your family. It's a shame when doctors refuse to look at the whole picture. It seems you have a very good handle on how all this stuff interacts. I bet you've been doing a lot of reading.
It's always a good idea to look at the digestive system first when iron deficient anemia presents in a male or post menopausal female. Once that's been ruled out, you look further.
The low ferritin might be due to his entire history and not just the thyroid issues. What he's been through would slowly be leeching his stores even if he didn't have thyroid issues on top of it. Problem is, once your ferritin stores are depleted, they must be built up again and usually that won't happen without supplements. With the complicated history he has though, that should be done under the guidance of a physician. In no event should he take iron supplements prior to the scopes. Perhaps a general practioner/family physician should be brought into the picture on that. They have a tendency to not focus on just one are of expertise.
It's possible that the insomnia may be from the lingering effects of the anxiety and stress. It's very hard to sleep when you've got a million worries running thru your head. What I'd suggest there might be melatonin or a mild sleep aid to break the cycle but again, that would have to be done under the direction of a physician.
Ok. Now that's a couple times I've mentioned guidance of a physician. Do you have someone orchestrating and overseeing all this? Someone you trust? It often takes one doctor who is involved in the whole process in order to sort out a mess such as this. That would be my next move. Find a good gp or internist to coordinate things and take care of the stuff that the specialists have a tendency to ignore. If you could find someone like that, I think things would go a lot smoother. You seem to have a good handle on things but you don't have the power and sway that an MD or DO has over all these specialists.
It's always good to have a good history. It's never annoying around here. But, like midwest said, thyroid lab results would be very helpful.
I wish you and your husband the best of luck.