I'm obviously not going to be able to diagnose what's going on with your husband but perhaps I can provide a little direction from my own personal experiences.  I'm a prostate cancer survivor (still have my prostate), have diabetes which I control through diet alone, and one other condition that I'll mention later.

My diabetes was diagnosed a couple of years ago and I was given a glucose/blood sugar tester by the diagnosing physician, and in my early days of knowing about it, I tested daily.  I no longer test that often because I know just about where it's at.  Yes, I think you are on the right track when you mention hyperglycemia, or high blood sugar.  All carbohydrates raise my BS significantly.  My clinic has me and all their diabetes patients on a high protein, low carbohydrate diet (no more than 15 carbohydrates per meal - 45 per day total) and that's what's allowed me to control it.  However, I'm human and I fall off that strict regimen from time to time and through testing I am very familiar with what raises it.  At this point, let me say that each person is different and what raises mine doesn't necessarily raise the BS of other diabetics, and mine isn't always consistent because eating carbos in the afternoon and evening raises my BS worse than in the morning.  What I've found is that bread, regardless of whether it is whole grain or white will raise my BS higher than ice cream, and oatmeal and potatoes will as well.  These things can take my BS to 185 to 210 at two hours after the meal, and normal is 120 or less.  Here is what I wish to pass on to you and that's that I've learned that often when the BS is elevated I do get a panic attack type of feeling, which relates to your husband's paranoia.  It doesn't happen each time, but it does happen.  Unlike your husband who gets tired, I get hyper, and my blood pressure generally goes up too.  (It's on the high side of normal anyway, much of the time.)  So, some of what your husband experiences is what I've experienced too.

A little over a year ago I went to a high school reunion and couldn't say no to all the carbohydrates - bread, potatoes, and cheese cake, two or three pieces.  When I got home I was in that hyper/panic attack mode and I checked my BS and it was 215.  Because I'd seen a study that said that apple cider vinegar can reduce BS levels, I started chugging that - at least three two ounce shot glasses full, washed down by water.  Checked my BS 30 minutes later and it was down to 85.  I still drink a lot of ACV and am unsure what effect it has on my BS, but on that occasion it worked.  Also, during that hyper/panic attack my heart pounded in my chest, something that has happened for decades after sweets and too many carbohydrates.  A couple of months after this particular experience I had the heart pounding episode again (not brought on by carbos) and saw my cardiologist and was eventually diagnosed with atrial fibrillation.  I know that I have had afib for decades too.  It explains a lot.  I had afib episodes quite regularly up to that point in time.  When they occur, my BP goes way down - because the heart is not pumping efficiently.

Long story short, after the afib diagnosis, I cut out all coffee including decaf, eventually quit all diet colas (diet cola for me can bring on the hyper feeling), and began taking kelp supplements.  The afib calmed down and within about six or seven months they quit completely and I haven't had an episode in a long time.  I credit it to the iodine because there have been studies that show there is a link between afib and iodine deficiency.

I would suggest that you get a glucose monitor - most physicians will give them to you free and you generally get a number of test strips free with it, and have him check his BS during those episodes after carbohydrates.  If the BS is over 140-150, some of what's going on could be that.  The other thing is to check his blood pressure during that time too (I always have a home monitor handy) and if his BP goes down, then it could be afib.  There are even some BP monitors on the market that will tell you if the heart is in fibrillation - mine does.  Afib reduces the blood flow to the body and can make you dizzy and tired feeling.  You can even check a person's pulse to see if they're heart is "skipping" a beat (actually it is extra beats, so it feels irregular).

Don't know if any of that helps but good luck in learning to control it.