Bunna, small amounts of sugars are okay because they don't cause cravings. We're talking about no more than 2 Tbsp. With that much half n half, you probably would have had cravings. What recipe was it? If it turned into something like 8 servings, it would have been fine.
I don't get why they are allowed, but they do seem to work. I don't get cravings from the Cool Whip Free, which is basically corn syrup and water.

I did not like the taste of the fat free half n' half, so I just use real half n' half the couple of times that I have wanted some in my coffee. Just a tablespoon of it, though, so I don't get too much of the bad fats.
It's a toss up...fats or sugars, with things like that. But for recipes, the evaporated milk is a great idea!