I'm afraid that one of the symptoms of my blood glucose being too low, or dropping fast, is irritability, lack of patience and sarcasm.
If I'm having a hypo, I can become incandescent with vicious, verbal rage.
And I cannot stop it. I watch it happening, and am unable to prevent the words coming out.
Physical violence is a real risk.
I find I am consistently happier and more relaxed when my BG is higher than ideal (but not 'high' - I'm trying to avoid talking numbers, because we are all different!)
If this is similar to your husband, then I completely sympathise - with both of you - mr B is a saint to put up with me, sometimes.
Assuming that the reasons for your husbands mood swings are the same as mine, the good news is that if he is able to keep his BG steady and at the lowish end of his usual range, his body will gradually adjust (mine does), and the mood swings will fade away. But it can be a bit stressful hanging around at the bottom edge of my BG range, feeling a little stressed, for days, waiting for the adjustment to happen. And I would imagine that it will be even more stressful for an insulin dependent.