I can't accept the concept of "space" expanding or curving no matter how well current theory matches measurement.

To me, "space" is simply a Cartesian xyz coordinate system (0,0,0 being undetermined) - the geometry of the universe.

When one asserts that "space" expands or curves they are implicitly referring to this geometry. Expansion or curvature can only logically be defined with respect to something.

What's contained in "space" and how it behaves is what our theories should try to describe.