This sweep runs the impulsive-diffusion Monte Carlo across the full radius range at once: impact parameters from the gravitationally focused encounter rate, velocities from a Maxwellian at dispersion σ, masses from the perturber mass function, and survival defined as eccentricity walking to the orbit-crossing threshold. The mass function carries a mass-segregated heavy-remnant tail (10 M☉ stellar BHs at the fiducial 1% number fraction, the fbh deeplink here), and that tail sets the floor: the median survival time is ≈3×10⁶ yr, roughly flat from 10⁻³ to 4×10³ AU, because the per-encounter kick variance and the encounter rate scale inversely with radius and their product cancels. This supersedes the stars-only ≈3×10⁹ yr floor Paper E first reported (recover it with fbh=0). The floor stays well above the 10⁶ yr passive-safety criterion, so flybys still never set the outer boundary; they are a trim budget, not a survival requirement.