Steven, I see your points, but let me clarify my perspective.

Determinism is not directly testable. But if physicists agree that the laws of nature (more on this in a moment) are deterministic--as those of quantum mechanics seem to be--then causal determinism at the macroscopic level is a logical entailment.

Regarding so-called "laws" of nature, I'm fine with the view that the best we can say is that they are so far unexceptionless empirical generalizations. But they stand, until and if we find exceptions.

More generally, I'm not a strict empiricist. That position is just as untenable as that of a strict rationalist. But I reject any metaphysical speculation that wanders too far from the empirical. I like to keep my metaphysics and epistemology very close, if you will. I really don't see an alternative.