You’re mostly criticizing preference utilitarianism (with the preferences being uninformed preferences at that), which is far from the only possible utilitarianism and not (I think) held by all that many people here.
It’s not a given that only happiness matters (on the face of it, this is false).
“Utilitarianism could be total or average” isn’t an argument against the disjunction of total and average utilitarianism.
You’re mostly criticizing preference utilitarianism (with the preferences being uninformed preferences at that), which is far from the only possible utilitarianism and not (I think) held by all that many people here.
It’s not a given that only happiness matters (on the face of it, this is false).
“Utilitarianism could be total or average” isn’t an argument against the disjunction of total and average utilitarianism.