The paper presents a comprehensive study of proton parton distributions (PDFs) using a symmetry-preserving formulation of a vector × vector contact interaction (SCI). The proton is treated as a quark + interacting-diquark bound state, with its structure derived from solving a Poincaré-covariant Fadeev equation. The study provides predictions for both unpolarized and polarized PDFs, including valence, glue, and four-flavor separated sea distributions. These predictions address various phenomena such as the asymmetry of antimatter in the proton, the neutron-to-proton structure function ratio, helicity retention in hard scattering processes, the charm quark momentum fraction, and the origin of the proton spin. The results are compared with available data, showing semiquantitative agreement in most cases, with mismatches attributed to the momentum-independence of the underlying interaction. The SCI framework offers a robust and insightful explanation of proton structure, providing both first estimates and checks on the validity of algorithms used in more sophisticated frameworks. The paper also discusses the evolution of these PDFs to experimentally relevant scales and their implications for various observables, including the neutron-to-proton structure function ratio and nucleon longitudinal spin asymmetries.The paper presents a comprehensive study of proton parton distributions (PDFs) using a symmetry-preserving formulation of a vector × vector contact interaction (SCI). The proton is treated as a quark + interacting-diquark bound state, with its structure derived from solving a Poincaré-covariant Fadeev equation. The study provides predictions for both unpolarized and polarized PDFs, including valence, glue, and four-flavor separated sea distributions. These predictions address various phenomena such as the asymmetry of antimatter in the proton, the neutron-to-proton structure function ratio, helicity retention in hard scattering processes, the charm quark momentum fraction, and the origin of the proton spin. The results are compared with available data, showing semiquantitative agreement in most cases, with mismatches attributed to the momentum-independence of the underlying interaction. The SCI framework offers a robust and insightful explanation of proton structure, providing both first estimates and checks on the validity of algorithms used in more sophisticated frameworks. The paper also discusses the evolution of these PDFs to experimentally relevant scales and their implications for various observables, including the neutron-to-proton structure function ratio and nucleon longitudinal spin asymmetries.