My entire point is that the "utility" of "utilitarianism" might need more complexity than the "utility" of economics, because if someone thinks they prefer a new toaster but they actually wouldn't be any happier with it, I don't place any importance on getting them a new toaster. IANAEBAFAIK economists' utility either would get them the new toaster or doesn't really consider this problem.

Agreed. For clarity, the economist's utility is just preference sets, but these aren't stable. Morality's utility is what those preference sets would look like if they reflected what we would actually value, given that we take everything into account. I.e., Eliezer's big computation. Utilitarianism's utility, in the sense that Eliezer is a utilitarian, is the terms of the implied utility function we have (i.e., the big computation) that refers to the utility functions of other agents.

Using "utility" to refer to all of these things is confusing. I choose to call economist's utility functions preference sets, for clarity. And, thus, economic actors maximize preferences, but not necessarily utility. Perhaps utilitarianism's utility - the terms in our utility function for the values of other people - can be called altruistic utility, again, for clarity.

ETA: and happiness I use to refer to a psychological state - a feeling. Happiness, then, is nice, but I don't want to be happy unless it's appropriate to be happy. Your mileage may vary with this terminology, but it helps me keep things straight.