The Gravitationally Active Spacetime Curtain (GASC), a unified framework is proposed where spacetime itself acts as a dynamic medium endowed with tension, a compressible root fluid, and repulsive anti-gravitons. This approach naturally resolves three fundamental problems in modern physics: black hole singularities transition to stable dark planets with finite-density cores, dark matter emerges from spacetime's density variations without requiring new particles, and quantum gravity becomes testable through anti-graviton-mediated interactions. The theory provides solutions for black hole structure, reproduces observed galactic rotation curves, and matches gravitational wave data from LIGO while predicting distinctive late-time echoes. Crucially, GASC makes testable predictions across multiple scales - from gravitational wave detectors like LISA, which could detect characteristic merger echoes, to particle colliders where missing-energy events would signal anti-graviton production. Unlike string theory or conventional dark matter models, GASC offers direct experimental verification through near-future observations while maintaining mathematical consistency with general relativity and quantum field theory. The framework presents a compelling alternative to current paradigms by unifying gravity, quantum effects, and dark phenomena through spacetime's intrinsic properties rather than hypothetical entities, bridging the gap between theoretical elegance and empirical testability.