Part III completes the three-layer architecture of State Locality Theory 2 (SLT-2) by providing a phenomenological framework that translates the structural ontology and effective dynamics of SLT-2 into concrete, experimentally testable predictions. No new free parameters are introduced beyond the localization constant α inherited from SLT-1. The document formulates an operational protocol for applying SLT-2 to real systems, constructs a regime map in mass–path-separation parameter space, derives quantitative visibility predictions for molecular interferometry, nanoparticle interferometry, and superconducting systems, and specifies falsifiability criteria. SLT-2 predicts gravitationally enhanced decoherence in the 10⁵–10⁶ amu range (ΔV ∼ 0.5–5%), suppressed sensitivity in superconducting phases, a pressure-independent visibility plateau in ultrahigh vacuum, and full coherence of neutrinos over astronomical baselines. The structural mass hierarchy is discussed honestly as a scale of node complexity, not a mass formula.