We present an exact mathematical formulation of cosmological orbital kinematics in a rotating Kerrspacetime anchored by an ultra-massive central core of mass MP = 7.82 × 1053 kg. In this configuration:1. The outer event horizon is situated at r+ = 122.764 Gly, and the cosmological matter disk is locatedstrictly outside the event horizon spanning radii r ∈ [122.764 Gly, 175.6 Gly].2. The Milky Way is located in the immediate exterior vicinity of the horizon at RMW = 123.3265 Gly,corresponding to a radial clearance of ∆r = +0.5625 Gly (562.5 Mly or a 0.46% fractional margin).3. The cosmic trajectory is traced continuously from the central Pivot (r → 0) up to the Milky Wayalong a self-similar, scale-invariant logarithmic spiral r(ϕ) = r0ebϕ.4. We demonstrate that the logarithmic spiral (and not the Archimedean spiral) trajectory can bemathematically equivalent to a geodesic; however, this is correct only in an effective flowingfluid metric as formulated in Sher (2017), whereas it is not valid as a geodesic in pure vacuumKerr or Schwarzschild spacetime.5. We enforce the strict dynamical equivalence condition vN (L) = vKerr, where vN (L) ≡pGMP /L isthe modified Newtonian velocity evaluated along the cumulative worldline arc length L, and vKerris the coordinate frame-dragging velocity at radial separation RMW.