You caution against arguing by definition and yet claim definitions that are not universally agreed on as authoritative. There is genuine confusion over some of these definitions, it's useful to try and clarify what you mean by the words but you should refrain from claiming that is the meaning. For example, contrary definitions of happiness (it's not just a brain state):

Happiness

state of well-being characterized by emotions ranging from contentment to intense joy

Good luck; good fortune; prosperity.

An agreeable feeling or condition of the soul arising from good fortune or propitious happening of any kind; the possession of those circumstances or that state of being which is attended enjoyment; the state of being happy; contentment; joyful satisfaction; felicity; blessedness.

good fortune; pleasure; contentment; joy.

Wikipedia

Philosophers and religious thinkers have often defined happiness in terms of living a good life, or flourishing, rather than simply as an emotion. Happiness in this older sense was used to translate the Greek Eudaimonia, and is still used in virtue ethics.

I don't think it's uncontroversial to claim that utilons can be increased by actions you don't know about either.

The definitions really are at issue here and there are relevant differences between commonly used definitions of happiness.