A major purpose of happiness is a difficult-to-fake signal to others of an outcome being good for me (rather, of it seeming to me to be good/desirable).
Happiness is what happens when I get what I want. Making happiness into the thing I want is almost completely backwards.
> Happiness is what happens when I get what I want.
Well, that's how it seems at first. But even though you were overjoyed at the presents you got on your 10th birthday, that happiness did not last. After seeing enough ups and downs, the mind might get tired of being endlessly pushed around by wanting or aversion. It might prefer to just be still, unmoved. Meditation helps develop this kind of stability.
And of course the happiness from getting things I want doesn’t last; if it did, my happiness would cease to be a useful signal for others of what I want, and therefore the mechanism which modulates my happiness would cease to usefully serve its purpose, which would be detrimental regarding the goal of me getting more of what I want.
Your arguments are all assuming that I terminally value being happy, and without that assumption they have no foundation.