Check out Gerson Therapy. You both can benefit from it. Since I do not know the study about hot/cold shower, I can only tell you my experience. I do hot/cold showers and it also makes me feel good. My doctor did ask me if I took supplements for testosterone, the answer was no. May be it is the hot/cold showers.
We do not know what your lifestyle is like so cannot comment, such as foods that you eat, exercise, mental stress, etc.
I personally feel radiation makes things worse, I have lost five relatives in last few years with this type of treatment and the suffering they went through after radiation was horrendous.
Iodine will certainly help your hubby, start slow and take all the co-supplements. But more so look at diet with micronutrients. Talk to doctor Furhman or MercolaIt. This will help you too. You said numbness on the left side, which can be blocked arteries or Insulin resistance.