We found out this year that many in my family have BeriBeri (thiamine or B1 deficiency) and we're now taking B1 shots.
The symptoms of BeriBeri are the same as the complications of diabetes. Benfotiamine is a synthetic B1 and is harder for the body to eliminate. It would seem that that's why it helps.
I am not a diabetic, but I've had idiopathic neuropathy for years. (We now know that it's from the B1 deficiency.) My neuropathy has improved ten-fold since I've started the shots. I do have some permanent nerve damage, but it's livable.
If I were in your shoes, I'd start my husband on Benfo right away. It can't hurt and has a good chance of helping. (I get mine from benfotiame.net) I've just started taking it myself.
PaMom