Finite Universe Cosmology, Part II: Self-Consistent Quantum--Gravitational Backreaction in a Finite Page--Flux Cosmological Model

We establish an executable two-stage quantum--gravitational backreaction construction for finite-universe cosmology. The first stage connects the exact fixed-Page owner of Paper I to the inherited native ten-coordinate Page operator. A charge-preserving map gives exact Page-form congruence and a uniform relative Hamiltonian-form bound below \(3.451×10⁻¹¹\) on the audited metric domain. On the certified Page10 actual-root sector, the ground-energy difference is below \(1.71×10⁻⁹\), the ground-projector distance below \(1.94×10⁻⁷\), and the phase-aligned state distance below \(1.366×10⁻⁶\). The moving-metric native extension uses a fixed Page calibration volume \(V_\) and a metric-dependent radial density. Its electric term factorizes exactly as \[∑ₙ{e_nᵉˡ(h)(2q-V_χ_n²S_1)^2}{8V_³}.\] The same formula is replayed from a compact excerpt of the authoritative production packet. The replay verifies the packet-level moving-volume/warp measure identity, the five explicit fixed-state metric derivatives, the profile derivatives of the electric square, and the same-state electric expectation. Total relaxed derivatives remain the sum of these explicit jets and the separately solved state/profile responses. The second stage is an independently audited interacting extension. One native finite Hamiltonian combines a 24-dimensional Page trial space, three vector and three two-form modes, 128 Gauss directions, and the complete retained contact and cross operators generated by one canonical elimination. The representative \(3{,}230{,}304\)-component joint state has Page reduced-state purity \(0.9657050494\) and largest Page eigenvalue \(0.9826705793\). Hence the maximum squared overlap with any pure Page--field product state is at most \(0.9826705793\), and the trace distance from every pure product state is at least \(0.1316412575\). This is a strict finite-state correlation certificate independent of the Page10 spectral bridge. Metric differentiation of that same state yields independent radial and tangential pressures and forces conjugate to internal and reduced-gravity variables. A signed joint response for the quantum state, ten Page widths, and radial profiles retains both the Schur tangent and the affine return of nonzero internal residuals and is returned to all \(9{,}946\) original finite residual rows. The representative nonlinear endpoint reduces five monitored weighted gravitational residual norms and sampled maxima while preserving positive sampled lapse and radial metric. Independent quadrature, source, held-out-profile, and occupation-complement diagnostics remain explicit. The result is an exact reference-volume Page bridge plus an independently certified correlated finite extension: together they furnish an executable, variationally closed backreaction architecture and a reproducible conditional endpoint for the declared Page--field system.