I've long since discovered that one can't get frostbit feet as long as the temperature is above 0° C. Sure feels like it, though. Not a fan of numb feet. A stopgap measure is toe warmers. I buy them by the case:
Amazon.com : HotHands Toe Warmers : Sports & Outdoors The real cure for cold feet in winter is winter MTB boots. I have a pair of Lakes. Wonderful but expensive.
I'm going back to my previous suggestion. I call it the drip method of feeding. No ups and downs, just constant carb calories coming in. The once an hour thing is hammering on your pancreas. For instance a Clif Bar: 250 calories but only ~43g carbs. I break them into 4 pieces and eat a piece every 15' minutes. Back when I ate solid food, I used to eat 6 of them on a double century plus rest stop food.
So that was a 4 hour ride: you were making good time, good for you. By the 60g/hour estimate, that would be 4 bottles of Ensure so you'd put 2 in your saddle bag. Don't get the Ensure Plus - it has more fat, which is what you don't want. My wife gets by on fewer calories, but you might need more.
As I ride, I look at the bottle - I always use translucent bottles - and see if I'm eating enough. At the rate you specify, a 480 calorie bottle would be gone in 2 hours or so. I'll guess that you don't really need that many calores - that'll probably get you 3 hours. So I'd look after an hour and make sure it was 1/3 gone.
The breakfast was light and then you didn't eat enough after. 400 calories is a number that's easy to remember for breakfast. Oatmeal is common: if you cook a cup of rolled oats, sweeten it up with lots of brown sugar, add butter and whole milk, you'd be pretty close. Half-and-half is extra marvelous.