Theoretical resonance energies for KLL dielectronic recombination into He-, Li-, Be-, and B-like Hg ions are calculated by various means and discussed in detail. We apply the multiconfiguration Dirac-Fock and the configuration interaction Dirac-Fock-Sturmian methods, and quantum electrodynamic many-body theory. The different contributions such as relativistic electron interaction, quantum electrodynamic contributions, and finite nuclear size and mass corrections are calculated and their respective theoretical uncertainties are estimated. Our final results are compared to experimental data from the preceding paper. The comparison of theoretical values with the experimental energies shows a good overall agreement for most transitions and illustrates the significance of relativistic electron interaction contributions including correlation, magnetic, and retardation effects and quantum electrodynamic corrections. A few discrepancies found in specific recombination resonances for initially Li- and Be-like Hg ions are pointed out, suggesting the need for further theoretical and experimental studies along these isoelectronic sequences.