For this example think of sitting in the top of a rocket.

While the force of acceleration on the capsule is provided by the rocket hundreds of meters below you the force on your body is provided by the seat that you are straped into. The force on the seat is provided by the capsule, which is provided by the rocket

Relativity has nothing to say about the form of the field in general. Whether the inverse square law applies in a given case is simply a consequence of the form of a particular distortion of space as it affects you. There is nothing in principle  stopping you from studying the local form of the field to make deductions about the source of the field. For instance, in a hollow sphere you would experience a flat field. If you were off to one side of a nearby slender, rod-shaped mass you would find that the inverse square law would only begin to apply when you were so far distant that you could regard that mass as amounting to a point mass.