It's interesting that your doctors are willing to do so many tests. Mine could clearly see my low MCV and I told him I had thalassemia and he just said everything is fine. He probably had no clue because he asked me if I drank a lot of alcohol (I don't) since my GPT was very high.
Edit: Were you able to let your GP do all the tests, including hormones? Or did you also meet with an endocrinologist? I'm not sure what I can expect from my GP.
Basically I went in there to checkup for my hormone stuff (same practice but not my usual doc), and mentioned "hey can you give me this test, I have possible genetic thal trait". She goes, yeah of course and took a look at my numbers (all my old tests are on file) and agreed it was worth looking into. We're pretty good here in Australia that most of this is covered by Medicare, even bloods, although for the hormone stuff, the GP's are always trying to shuffle me back off to endo's (which charge up to $350 a visit, plus extra for blood tests) as they don't want to advise on stuff that aren't their specialty. I've got it down well enough though that as long as I get bloods and GP check ups, I can usually adjust my regimen to suit myself.
Anyway, the lab rang my doc and then she rang me, saying they should do a gene test as the electro test only showed expected hemo variations and levels which didn't catch the first 80% of thal, but they needed my consent as the gene test to catch the last 20% isn't covered by Medicare. All told it would cost me 100 bucks. So of course, I said. Still waiting on that one.
I did a bit of quick research and found plenty some situations alike mine - still mutated thal genes but with low or normal A2 hemo, both of which could either be alpha or beta. "Silent" thal they had named it, as unless you knew you were looking for thal, you'd get the A OK on those numbers and look elsewhere for the problem.