My GTT showed what some might call my sugar intolerance very clearly. They sent in a diabetic nurse to advise me. Her advice: "Put a log on the fire. Carbs are like tinder, you go through them too quickly. Eat cheese."
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This is exactly how I also got into it - eating snacks at work, which was somewhat physical. This was back in the day when eating <10% fat was all the rage, so I was carb snacking. It's still a problem for me somewhat, though now if I eat too much of the wrong thing, I can simply wait for the drop to pass and then I'm alright. I've learned not to try to eat my way out of the drop. Fat burning will take over and bring it back up now if I just wait.

Suggestion: My type 1 diabetic friends told me that one's blood sugar is most stable in the morning before one has eaten. Thus it's a good practice to go for a 1-2 hour pre-breakfast ride, fasted. If that's not possible, then do it any other time when it's been a few hours since you've eaten. This improves one's ability to move fat from adipose tissue to the muscles, and makes it easier to deal with times when one's blood sugar will start to drop. I do this fairly often, eating nothing before the ride. I'll sometimes get a transient hypoglycemia after a while, but that passes. After 2 hours, I can feel my power start to drop. That's not hypoglycemia the way we normally experience it in our non-riding life. It's the muscles crying for fuel. I always take a bottle of sports drink with me on any ride, just in case, and at ~2 hours I'll need to start taking a few swallows or give up any idea of performance riding. Some people can go for longer, but it's not necessary IME. Whenever I ride, I wear a heart rate monitor. I've been doing that for almost 20 years, so I have a good feel for the data. During a ride, if my heart rate starts to drop at a hard effort level, that's a sure sign I need to eat carbs. I won't feel hypoglycemic.

On any serious ride, it's impossible not to eat carbs. I know a lot of riders and there isn't anyone among them who doesn't eat carbs on a long ride. On a recent bike tour, we had a committed low carb Paleo rider who was eating sandwiches big time by the 3rd day. We also had a vegan who was eating liver and ribs.

My wife and I just rode RAMROD yesterday on our tandem - 150 miles and 8800' of climbing. I drank 1500 calories composed of 85% maltodextrin (GI >100) and 15% whey protein, plus a big sandwich and a couple cookies. My wife drank 1440 calories of Ensure, which has a similar chemistry to my drink, plus the sandwich and cookies. Strava estimates that we burned ~6150 calories for ~2300 calorie deficit. Seems about right. Two hours before the ride, we each drank ~400 calories of my malto/protein mix, no other food. Neither of us experienced any hypoglycemia even though I'm susceptible to it. The weird liquid food is because it's very difficult for us to digest anything else when climbing hard in the heat.

I believe that our problems, caused by eating carbs frequently while working or in your case, power walking, fall into a different category than eating carbs while riding or running hard. In these latter cases, energy use is scouring out the sugar from our blood faster than we can replace it no matter how much sugar we ate. This "scouring out" limits insulin release because our blood sugar stays relatively low. Thus the "reactive" component never happens. The body fills that gap with glycogen and fat. So the whole time you're riding hard, you're already getting energy from sugar: glycogen. It's pouring glucose into your system as your exercise level requires it to do. No difference between that and eating it, except that eating it spares glycogen for later use. It's the rate of glucose use by the muscles that eliminates RH during exercise.

There's a very good question: Why doesn't glycogen release during hard exercise keep the muscles fueled and eliminate any need to eat carbs before that ~2000 calories of stored glycogen are gone? I don't know the answer to that.