Two-dimensional materials and their heterostructures have opened up new possibilities for magnetism at the nanoscale. In this study, we utilize first-principles simulations to investigate the structural, electronic, and magnetic properties of Fe/WSe2/Pt systems containing pristine, defective, or doped WSe2 monolayers. The proximity effects of the ferromagnetic Fe layer are studied by considering defective and vanadium-doped WSe2 monolayers. All heterostructures are found to be ferromagnetic, and the insertion of the transition-metal dichalcogenide results in a redistribution of spin orientation and an increased density of magnetic atoms due to the magnetized WSe2. There is an increase in the overall total density of states at the Fermi level due to WSe2; however, the transition-metal dichalcogenide may lose its distinct semiconducting properties due to the stronger than van der Waals coupling. Spin-resolved electronic structure properties are linked to larger spin Seebeck coefficients found in heterostructures with WSe2 monolayers.