Has he ever had any endocrine hormonal testing during this time?
I would say your husband needs some blood testing for , FULL BLOOD COUNT, DIABETES, AND THYROID PROFILE.
I have thyroid disease and i can get night sweats, it sounds to me like this could be the endocrine system, causing this problem, so i would have the tests to rule out if its endocrine like thyroid etc.
You can get sweats and go confused with diabetes,
Also get your husband to have an IGE blood test for allergies, when the problems arise again.
Good luck
Nicola