Cheryl,
My experience being on synthroid since last summer (started at .25) is that you really have to wait at least 6 weeks before you know what it is going to do to you. Actually 8 weeks is better. I did not believe that at first, but now that I am finally adjusted I do. It might have been better if your husband started slower at .25 which is just a diagnostic dose really, then moved to the .50, but ok, so his body is having hot flashes at .50: that may just be a temporary reaction. Synthroid is not a "take one and you'll be fine in a week or two" kind of medicine. I guess some may have it easier but lots of us have to go through several months of upward adjustment before you feel good. Even after you are at the optimum you may have to wait another 2-4 months before all the symptoms vanish because your body has to heal. Your husband's TSH, while higher than it should be, is low compared to what mine was--try 52. So maybe it won't take him as long.
I felt better after being at the .50 dosage for 6 weeks but not really good, same at .75, etc.

I got impatient too, so I do understand.
Anne