But this introduces at least one more premise before we get to Aquinas' conclusion: the premise that "physics cannot in principle capture all there is to physic

But this introduces at least one more premise before we get to Aquinas' conclusion: the premise that "physics cannot in principle capture all there is to physical reality". And that is not enough, as even if it could be sustained, Feser is still arguing from a generality to a specific. Physics might fail to capture all there is to physical reality while it also being the case that atomic decay is acausal. Furthermore, when Feser writes: "In short, anyone who claims that quantum mechanics undermines Scholastic metaphysical claims about causality owes us an alternative worked-out metaphysical picture before we should take him seriously", he is just attempting to shift the burden of proof away from those on whom it properly rests: those who say that they can prove there's a God. Then there's the straw man "If the critic, like the early Russell, denies that there is any causality at all..." that we need not waste any time on. - And that's all just from the short quote you have provided! What Feder is not delivering here is an argument that the decay of an atom had a specific cause that operated at a specific time. Aquinas at least has the virtue of being straightforward, but there's still the independent issue of the unstated assumption that I raised earlier.