“As a practical matter it seems to me that Epicurus was right that it would be impossible for us to live happily if we did not organize our lives as if we are confident that we have some amount of free agency. … That has to be good enough and I judge it to be good enough - at least for me.”
– Cassius post #4 above.
Yes. And the fact that our agency / ability to choose may be constrained by circumstances or our own abilities at any given moment is no refutation.
Even under a regime of strict determination, that very regime, it seems to me, includes for us the near-universal perception that we have such agency – and the practical necessity that we behave accordingly in order to live happily.