Blaze, I am on limited time at the moment so will answer what I can in a quickie session for now.
DH is intensely itchy, so itchy it consumes your entire mind, so itchy it is called the suicidal itch. It's a 30 on a scale of 1 to 10. Having said that; i will say that we don't know everything about dh. Perhaps, just perhaps you have dh & it's in the infantile stages & perhaps, just perhaps, the intensity is less in the infantile stages for some people. I will also say that celiac disease is associated with any # of skin conditions/rashes.
Steroid use within 2 or 3 months, either topical or oral will cause a false negative in either skin biopsy for dh or in celiac blood panel. I can provide links to back up what I say but will have to find them as I am a poor bookmark organizer so will have to check back later with those links.
As to your #3: Personally, I'm not so sure about those patch tests but that's just MHO. You could use latex gloves for 30 years & have no problem & then 1 day you develop an allergy to it. Especially if you have celiac disease. We tend to develop allergies to things.
As to your #4: I have read the same thing. In MHO I don't think that would cause migrating rashes.
As to your #5: I am concerned when you say "avoid" gluten. If you are going to test it then you can not just avoid gluten; you have to be rabid 1000% gluten free otherwise you are wasting your time. And I will warn you that if you find you still believe you have dh & want to do a gluten challenge then you may break out like never before. Also, you will have to be actively consuming a normal gluten diet (not a light gluten diet) in order to have a dh biopsy done.
I read your post on the Dapsone thread yesterday & was going to respond but unexpected events occurred here which prevented me from responding prior to now. I agree with the testing the derm wants to do before & while you are on Dapsone. Those are good things!
You mention the rash appearing one week on 1 clavicle & the next week on the other. DH does like to present bilaterally or "ghosting" on opposite sides of the body in the same location. But it doesn't always present that way.