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This paper investigates D-brane dynamics and tachyon condensation in a non-supersymmetric RNS string framework, with particular emphasis on the emergence of Standard Model (SM) gauge symmetries after compactification. We analyze the distance-dependent interactions associated with D-brane separation and their possible implications for the effective Coleman–Weinberg potential. When branes coincide, additional massless open-string states appear, enhancing the gauge symmetry and modifying the vacuum structure. Tachyon condensation can subsequently alter the spectrum and provide a mechanism for symmetry breaking and mass generation, with features analogous to the Higgs mechanism. The gauge symmetries are related to the isometries of the compactification space, while the resulting Kaluza–Klein spectrum is governed by the compactification geometry and scale. We further show that the threefold fermionic multiplicity associated with the three generations is already incorporated in the degree-of-freedom counting and does not introduce an additional factor into the ten-dimensional zero-point-energy cancellation. Under the stated representation-preserving assumption for the excited-state tower, the cancellation extends to the corresponding oscillator levels. These results illustrate how a non-supersymmetric string construction may accommodate the gauge and matter structure of the Standard Model while providing a framework for studying the interplay between brane dynamics, tachyonic instabilities, compactification, and symmetry breaking.