My challege is that you are clueless wrt understanding relativity and the general purpose of models created to describe physical phenomena. Returning to Patrick Reaney's words
"Einstein's concept of space-time
is free creation of his mind. It does not need
to represent a THING ontologically, and thus
there is no circular reasoning. Einstein invented a
concept and then assigned properties to it that
either worked to fulfill the goals he wanted it
for, or they do not. Period. Your notion of circularity
is asinine. All you are really talking about is
self consistency: That is, Einstein's concept of a
"spacetime" is consistent with the principles
used to define it and with the experiments done to
test it. No better praise can be given any theory
in physics!!!! Roger S. Jones called it "stacking
the deck," meaning that we invent those concepts
(including models, even abstract ones) that fulfill
the end results that we already know about. That
is precisely why physics is not about true models,
but about the free invention of theories that work.
As far as anyone can tell using physics, there is
no such thing as "spacetime." Spacetime is just
a theoretical abstract model useful for building
a theory thereon.
In GR Einstein was out to build a relativized
version of a gravitational field that reduces to
Newton's in the appropriate limit. So, of
course, there is some "stacking of the deck"
in this effort. But it is logically valid and
effective. Thus the effective use of a model
of spacetime does not prove anything about
"real" spacetime, what ever that is. But it
does prove that the abstract model is useful.
When you say Einstein made an error wrt to the parameters of his model then you must show how it doesn't do what he intended it to do. This means provide an experimental result which conflicts with a prediction of the model. Any high school physics student should know this, so what is your problem?