This is the definitive paper on the derivation of G. Starting from the proton mass (itself derived from the 600-cell eigenvalues), the gravitational coupling αG = α¹⁸ × 12/7 is derived with zero gravitational input. The full chain: μ + mₑ (from the Rydberg constant) → mₚ → αG → G. No measurement of gravity is used at any point. The derivation uses only electromagnetic measurements (α, mₑ from Rydberg) and the geometric structure of the 600-cell. G emerges as a consequence of electromagnetic confinement — not as a primitive constant.