Plastic deformation in crystalline metals is governed by the motion and interaction of dislocations. In recent years, understanding size-dependent behavior at the small scale has become increasingly important, as mechanical responses often deviate significantly from bulk predictions. To capture such mechanisms at the microscale, we employ a defect dynamics modeling(DDM) framework that directly couples discrete dislocation dynamics (DD) with the finite element method (FEM). This concurrent scheme allows us to integrate the strength of DD in simulating dislocation behavior with the capacity of FEM to handle larger scales, boundary conditions, and loading modes. Our model accurately accounts for both short and long-range elastic interactions, while improving computational efficiency compared to conventional DD simulations. By implementing an atomistically informed dislocation nucleation scheme, we can directly investigate defect initiation from voids, cracks, and surfaces under complex stress states. In addition, the framework incorporates plastic strain regularization and crystal rotation effects to ensure physical consistency across scales. Validation against analytical solutions and traditional DD confirms the accuracy of stress and interaction force calculations. Example applications, including micropillar compression, torsion, and void growth, demonstrate the predictive capability of the coupled model. Overall, this work provides a unified computational approach to explore small-scale damage evolution, bridging dislocation mechanisms with continuum-level constitutive responses.