Reliable prediction of lunar regolith mechanical behavior is essential for exploration and infrastructure development, particularly in permanently shadowed regions where water ice likely exists. This work develops and validates a high-fidelity DEM framework that combines realistic non-spherical particle morphologies and a flexible membrane boundary to study the effects of ice content, initial density, and gravity on regolith behavior. Model parameters are first calibrated for dry regolith by matching angle-of-repose trends across gravity levels and by comparing triaxial responses against laboratory data. The framework is then extended to ice-bearing regolith by introducing parallel bonds to represent ice cementation over representative content ranges. Triaxial simulations quantify macroscopic responses and microstructural evolution. Results show that increasing ice content markedly elevates peak strength, while promoting stronger anisotropy and localized deformation. The study highlights a dual implication of ice: enhanced load-bearing capacity but reduced ductility, with practical relevance for trafficability, foundation design, and excavation on the Moon.