But if we could manage to magically "freeze time" then we would find ourselves in one position in configuration space where the particle is unambiguously in one position (let's say the left slit).

It is not my understanding (I am a layman) that this is an appropriate statement to make: I don't think that even the frozen-time point would show the particle to be in a discrete position. I tend to the belief that the 'wave' portion of quantum wave/particle duality represents the many probabilities co-existing within our physical universe. I'm aware this disagrees with the basic Bayesian assumption of non-frequentism, but I'm not prepared to get into that argument at this time. (I tend towards Bayesian thinking in all other ways, just not on this point.)

Anyhow -- the point is, while when discussing the exact manners in which a given particle can interact with others, it is only relevant to discuss its particle-nature; when discussing its opportunities to interact, it is only relevant to discuss its probability-spaces. As multiple probabilities tend to interact by forming subsets of available probabilities, and as 'larger scale' physics is composed definitionally of complex systems, this would tend to 'factor out' towards the blissfully deterministic-appearing world we see in the "Middle World".

The consequence of this notion, however, is that as the Cat/box system has a radioisotope whose decay triggers the release of the toxin; the presence of both possibilities means that the system at the Newtonian scale will behave as though the isotope had decayed. In which case, you've got yourself one dead cat.

I am quite certain that someone of greater expertise would rip this comment to shreds, and I invite the opportunity to be educated. :)