My point is that whilst the velocity of that precisely located particle may be somewhat smeared, the consequences of that particle's interaction with whatever it collides with will be identical every time you rewind-and-replay the universe.
Unfortunately, without being able to rewind and replay the universe, or at least build a sophisticated enough model the represent such an event, we'll never know.
So on the one hand you are stating the consequences will be identical and then you are saying we don't know.
I think, again, that there is an issue when it comes to quantum mechanics of trying to interpret the phenomena in an every-day kind of experience and logic. The idea that if two starting conditions are the same then the outcome must be the same comes from classical physics, as does the concept of determinism.
If a particle of given position does not have a defined momentum then how can the starting conditions be replicated even in a temporal rewind when those starting conditions are fundamentally uncertain?
Not quite. I'm saying "we'll never know", which is different from "I don't know"; i.e. it is unknowable.
Re the thought experiment of replaying the universe; we are not "replicating" the universe. We are imagining that the universe is "reset" and played again. Think of it as an outside observer (yeah, I know, the observer influences the observed...) who gets to travel back in time and watch the universe unfold again. If we accept the observer is only there for the sake of the thought experiment, but not there for the replay in reality, what agent will cause the universe to play out differently? Saying "we can't rewind the universe" misses the point of the experiment; the whole point is that we have (somehow) and the observation is on the replay. Anything less than a perfect reset invalidates the experiment so can be ignored, at least for our discussion of free will...
Let me ask the question in reverse; if the universe were to be rewound and replayed, with all starting conditions identical, why would anything different happen? I'll go back to Occam; will the universe replay, or will some unknown property manifest and change things?
If we accept that matter, at the quantum scale, has wave properties, that's fine since those same properties are present in any subsequent repeat play. In fact, by definition, those properties are identical! We can't calculate some of the states of those properties, but since they are identical, then what exists to make the outcomes different?
Uncertainty is a human concept. All it does is put a marker up to declare the limit of our knowledge; it is not an actual "force" or agent that exists in the physical world.