This arXiv preprint (not yet peer-reviewed) introduces a mechanism where realistic interstellar medium density structures, drawn from TIGRESS-NCR magnetohydrodynamic simulations of Milky Way-like conditions, drive stellar orbital heating and radial migration through gravitational perturbations. Unlike prior models treating the ISM as compact spherical clouds, the study integrates test-particle trajectories in time-dependent, high-resolution density fields, revealing heating scalings of sigma_R proportional to t to the 1/2 at early times for cold orbits and t to the 1/5 later for warmer ones—departing from the classic t to the 1/3 expectation from transient spiral scattering. Radial migration reaches over 30 percent of solar-neighborhood levels without invoking stellar spirals, yielding an unusually low heating-to-migration ratio of rms delta J_R over rms delta J_phi approximately 0.055. Vertical motions damp amplitudes but preserve scalings, all consistent with quasilinear diffusion theory for dominant fluctuations at lambda star around 600 pc and tau star around 70 Myr. The work reframes disk dynamics by showing ISM structures alone can dominate transport, a factor traditional N-body models have underestimated. Limitations include the absence of live stellar spirals and restriction to test particles rather than self-gravitating stars; results rest on simulation resolution and assumed Milky Way conditions without direct observational calibration. Related analyses appear in Sellwood & Binney (2002) on action diffusion and Kim et al. (2020) validating TIGRESS ISM physics, both underscoring how non-axisymmetric gaseous features alter secular evolution beyond pure stellar scattering.