Determinism states that it is impossible for us, to choose otherwise than we do.

This is a truth with certain reservations. It is true, that once the choice has been made, it was always impossible for us to choose differently, because the choice has been made, making it the only choice, or "no choice".

So one can argue that the past could never have been different than what it became.

But, from the present, we experience a multitude of options. In the present, we are given choice and so have free will.

If an entity has knowledge of the distant future, to this entity everything is determined. To every other entity, (me and you) it is not so.

In this way, and this way only (as far as I can discern) determinism and free will can coexist.

So in essence, free will and determinism is a function of time (or rather, time-perspective), and time is a function of space (time is change, and only space can change).