hmmmm - now I smell something. Seems the unit became involved in deciding your medical care which shouldn't happen (yes I know it does, been there myself and it wasn't pleasant, I lost the battle but it worked out good for me in the end. Sometimes the meddling works out despite their evil intentions
). You're doc at the CDU is your primary care giver and should be determing your periods. If he can not approve longer than 14 days but believes it should be 30 days then he should go to the next level for approval. I would check with him on that. It may be though that the unit already got to his boss and that is why he is restricted to the 14 days now.
You were right to stick to the 30 days - the Maj does not have the authority to revoke sick leave you are granted. The CDU didn't contact you with an amendment so it was still valid.
heat rash - fungal infection, 9 years? Wow.
Chin up and keep your powder dry.