Multidomain dynamic manipulations for terahertz (THz) absorbers usually necessitate the orchestrated actions of several active elements, inevitably complicating the structural design and elongating the modulation time. Herein, we utilize the coupling between the total reflection prism and electrically-driven MoS2 to activate a tight field confinement in a deep-subwavelength interlayer, ultimately achieving frequency-agile absorption adjustments only with a gate voltage. Theoretical and simulation analysis results indicate that the redistributed electric field and susceptible dielectric response are attributed to the limited spatial near-field perturbation of surface plasmon resonances. We also demonstrate that perturbed MoS2 plasmon modes promote the formation of dual-phase singularities, significantly suppressing the attenuation of the absorption amplitude as large-scale frequency shifts, thereby extending the relative tuning range (WRTR) to 175.4%. These findings offer an efficient approach for expanding the horizon of THz absorption applications that require ultra-broadband and swift-response capabilities.