Abstract We present the complete dynamical formulation of S21 Theory, extending the topological framework established in [Bachani, Zenodo 2025] to include explicit field equations for all sectors of fundamental physics. Working on the 21-state vacuum manifold M₂₀ ∪ {σ} derived from a 6-bit lattice with icosahedral A₅ symmetry, we construct the discrete action principle governing fermions, gauge fields, the Higgs sector, dark matter, and gravity. The field equations take the form of operators on the graph: a discrete Dirac equation for fermions, lattice Yang-Mills equations for gauge bosons, a graph Klein-Gordon equation for the Higgs field, and an isolated oscillator equation for the dark matter singularity χ. Gravity emerges from variation of the discrete curvature functional R[w] with respect to edge weights and node volumes, yielding graph Einstein equations that couple geometry to the discrete stress-energy tensor. We demonstrate the continuum limit explicitly: as the lattice spacing a → ℓ_Pl, the discrete actions converge to the Standard Model Lagrangian plus Einstein-Hilbert gravity, with corrections suppressed by powers of a·M_Pl. Newton's constant G emerges from the Ω₊ ↔ Ω₋ vacuum mixing amplitude (States 63 ↔ 0), not as an input parameter. Verification comes from black hole analysis: mapping Reissner-Nordström and Kerr geometries to the 6-bit state space reveals that spacetime inside the inner horizon collapses to the maximal state Ω₊ (State 63), with 99.87% fidelity across 4000 radial samples. The Bekenstein-Hawking entropy formula acquires a topological correction: S = log(21) × A/4ℓ²_Pl, reflecting the 21-state vacuum degeneracy. The framework makes falsifiable predictions: tensor-to-scalar ratio r = 0.003 and spectral index n_s = 0.946 for inflationary perturbations, testable by LiteBIRD; and effective neutrino mass m_ββ = 3.8 ± 0.5 meV, testable by nEXO and LEGEND. Combined with the JUNO-verified neutrino mixing angle from the companion paper, S21 Theory now constitutes a complete, predictive unification of quantum field theory and general relativity from pure discrete topology. Keywords: quantum gravity, discrete geometry, unification, Standard Model, lattice field theory, black hole thermodynamics