Topological interface states in open photonic systems combine spatial localization at domain walls with temporal confinement characterized by a radiative quality factor. Here, we develop a non-Hermitian Dirac formalism for surface-emitting Jackiw-Rebbi states in dielectric metagratings. We show how varying the local amplitude of the lattice perturbation shapes the complex Dirac mass profile, enabling control over the quality factors and far-field radiation patterns of the interface states, while preserving their topological character. Applying this framework to a metagrating with second-order Brillouin-zone folding, we design a spatially graded superlattice perturbation that supports interface states with quality factors exceeding 10⁴ and Hermite-Gaussian beam emission. These results establish superlattice perturbations as a strategy for topological beam shaping and offer a route toward high-Q topological surface emitters.