so I deliberately and arbitrarily mark a point on a blank piece of paper and a moment in time say 10 am.
1/ How can the precise location and time of the point be determined given infinite reduction to zero?
"Infinite reduction to zero" is irrelevant.
The precise location and time of the point can be determined because it is the conclusion of a deterministic process.
It doesn't mean that we, as humans, can predict the conclusion.
It doesn't mean, in that sense, that we humans can "ascertain or establish by research or calculation" (per the definition Google offer up) but it means that the conclusion has been caused to occur in a deterministic fashion - i.e. the result of cause and effect according to processes where an input leads to one possible output.
If the same input can lead to multiple possible outputs then the process is not deterministic.
2/ How could any one predict including me the exact location and time given infinite reduction to zero?
Prediction in a practical sense is not relevant.
Conceptually, however, if one could know the initial state and the governing laws, and one could process the information faster than it actually plays out, then one could predict the output.
Yet the mark has been made by me and only me and exists regardless of incapacity to determine it's exact location or time.
You are confusing notions of determinism and practical predictability.
If one knew the initial state and the governing laws, one could predict the outcome.
They can do this because in a deterministic universe the outcome is determined by the initial state and the governing laws.
3/ How could any thing other than the actor determine it's location and time given infinite reduction to zero?
"Infinite reduction to zero" remains irrelevant.
The outcome, the time and location, is what it is because the process that gave rise to it resulted in it, the way that a clock tells the time because of the process that turns the hands etc.
There is, as iceaura repeatedly mentions, vast levels of complexity between the clock and a person but the principles remain the same.
Keeping in mind that I chose the location and the time to place my mark.
No one disputes the process of choice being carried out.
The issue at hand is whether it was free.