Nevertheless I have talked about all nows in acknowledgement of possible differences.
I'm obviously not getting this across. I assume by all 'nows' you mean god would know everything about every observer's now. Here is the problem: if we consider one reference frame at one point in time - call it X - then the immediate future of X (say X in ten minutes time) is already in the past of another (equally valid) reference frame.
There is an example that illustrates the point. If two people, A and B, walk past each other on Earth at a time T, their relative velocities mean that what happened simultaneous to T in the Andromeda galaxy in A's reference frame differs from B's reference frame by several weeks*. So if T is 'now' - when is the 'now' in Andromeda that an omnipresent (but time located) god would be aware of?
It all makes sense for located observers because of the causality structure of space-time - no information can travel faster than light. An omnipresent observer screws that up bigtime and leads to contradictions. Information travelling faster than light leads to the same sort of problems as time travel (because it
is time travel in a sense).
What I don't find clear is whether any location has an actual future and whether that future actually exists. Therefore my general point is that the future does not exist even for an omnipresent observer.
Are we perchance in agreement.
As I put in a footnote in a previous post - there really is no concept of a now in any fundamental physical theory. Even in Newtonian physics, 'now' has no more status that 'here'.
General Relativity stands as
the theory of space and time (and it is very well tested) and it treats space-time as a manifold. Space and time are not separate - there is no flow of time and no 'now'. It's sometimes referred to as the 'block universe' picture, where all of space-time (the manifold) just is.
Of course, GR is still to be reconciled with quantum field theory so it isn't the last word, but the evidence supporting it means that it is at least a very, very good approximation to how space, time and gravity work.
* I don't guarantee the exact figures - I haven't done the sums or looked it up again - and I'm working from memory.