This paper investigates the deployment of a cost- efficient fiber-wireless (FiWi) access network with joint utilization of fixed wireless access (FWA) and fiber-to-the-home (FTTH) technologies. In this work, we consider that residential users over a geographical area are to be provided with network services, constrained by the available network resources. We explore the implementation of hybrid FiWi access network that integrates a fiber-based passive optical network (PON) and fifth-generation (5G) wireless access network to provide efficient network services. This paper proposes a methodology for topology optimization of FiWi access networks, considering the usage of three dimensional (3D) beamforming and 3D resource grid for downlink transmission from the gNB to the users in 5G scenario. We derive the beam codebook and generate multiple beams to simultaneously serve the spatially separated users. We derive the closed-form expression for millimeter-wave channel model incorporating large-scale and small-scale parameters to compute the effective SINR of users. Further, we propose an optimization framework for optimal resource allocation (i.e., beam and resource block) by utilizing the 3D resource grid for downlink transmission. We perform extensive simulations to demonstrate the effectiveness of the proposed methodology for various 3GPP 5G outdoor propagation scenarios, viz., RMa, UMa, and UMi-street canyon.