The Fine Structure Constant as a Dynamical Fixed Point of K = 1 Geometry

We present an extended analysis of the fine structure constant within the K=1 chronogeometrodynamic framework. The core formula is alpha^{-1} = 32 pi^2 * eta(C*, D*) where eta is the phase-compensation fraction defined from the eigenvalue spectrum of the symplectic generator J_G = G^{-1}J, and (C*, D*) is the dynamical coupling-damping point selected by stability optimization. The original result alpha^{-1} = 32 pi^2 eta_opt (where alpha denotes the electromagnetic fine structure constant throughout) is subjected to systematic independent verification across 6 exploratory grids (each using a fixed pool of 300 Hessians evaluated across 12 simulation configurations; 1,800 unique matrices total) and a controlled 132-point (C, D) scan evaluated on a shared pool of 200 Hessians (26,400 evaluations). We find that eta_opt is NOT a parameter-independent statistical invariant as originally claimed, but rather a function eta(C, D) of the dynamical coupling C and damping D. However, this dependence is itself physically constrained: three independent stability metrics -- minimum median Var(K), maximum restoration gain kappa, maximum Quality Q = kappa x tightness -- all converge to (C*, D*) = (0.1, 1.0) on the full coarse grid. This point passes all identifiability gates, yielding a/b = 0.756 (0.8% from 3/4), eta_opt = 0.4307, and 1/alpha = 136.0 (0.8% from the CODATA 2018 value alpha^{-1} = 137.035 999 084(21)). The neighboring point (0.2, 1.0) confirms with a/b = 0.753 and 1/alpha = 135.7. Local refinement beyond the first pass is ongoing; preliminary fine-grid scans suggest modest shifts consistent with the constraint-ratio hypothesis (deviations at the few x 10^{-3} level from CODATA; details in the main text). Sensitivity of the fitted a/b to simulation hyperparameters (sigma, dt) is observed; a principled noise model remains an open gap. This multi-metric convergence constitutes strong evidence for an independent selection condition free of circular reasoning.