This paper presents a comprehensive study of proton parton distribution functions (DFs) 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 determined by solving a Poincaré-covariant Faddeev equation. The study provides predictions for unpolarised and polarised DFs, including valence, glue, and four-flavour separated sea components. These predictions are compared with existing data and QCD-kindred results, showing good agreement in many cases. The SCI framework is found to be robust and insightful in explaining proton structure as expressed in DFs. The paper outlines the derivation of formulae for the SCI calculation of hadron-scale proton flavour-nonsinglet (valence) DFs. It discusses the algebraic formulae for helicity-independent and helicity-dependent DFs, highlighting the role of diquark correlations in the proton wave function. The results show that the SCI predictions for proton DFs are consistent with QCD-based expectations, particularly in terms of the large-x and small-x behaviours of the DFs. The study also presents results at the hadron scale, showing that the SCI predictions for the proton's valence quark DFs are broadly consistent with realistic DFs and other theoretical models. The predictions are then evolved to experiment scales using the AO scheme, which has been shown to be effective in many applications. The evolved DFs are compared with data and other theoretical predictions, showing good agreement in many cases. The paper also discusses the implications of the SCI results for the proton's spin, the asymmetry of antimatter in the proton, and the origin of the proton's spin. The results suggest that the SCI framework provides a sound and insightful explanation of proton structure as expressed in DFs. The study highlights the importance of diquark correlations in the proton wave function and the role of Pauli blocking in explaining the asymmetry of antimatter in the proton. The results also show that the SCI predictions for the proton's DFs are consistent with modern data and other theoretical models. The study concludes that the SCI framework provides a robust and insightful explanation of proton structure as expressed in DFs.This paper presents a comprehensive study of proton parton distribution functions (DFs) 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 determined by solving a Poincaré-covariant Faddeev equation. The study provides predictions for unpolarised and polarised DFs, including valence, glue, and four-flavour separated sea components. These predictions are compared with existing data and QCD-kindred results, showing good agreement in many cases. The SCI framework is found to be robust and insightful in explaining proton structure as expressed in DFs. The paper outlines the derivation of formulae for the SCI calculation of hadron-scale proton flavour-nonsinglet (valence) DFs. It discusses the algebraic formulae for helicity-independent and helicity-dependent DFs, highlighting the role of diquark correlations in the proton wave function. The results show that the SCI predictions for proton DFs are consistent with QCD-based expectations, particularly in terms of the large-x and small-x behaviours of the DFs. The study also presents results at the hadron scale, showing that the SCI predictions for the proton's valence quark DFs are broadly consistent with realistic DFs and other theoretical models. The predictions are then evolved to experiment scales using the AO scheme, which has been shown to be effective in many applications. The evolved DFs are compared with data and other theoretical predictions, showing good agreement in many cases. The paper also discusses the implications of the SCI results for the proton's spin, the asymmetry of antimatter in the proton, and the origin of the proton's spin. The results suggest that the SCI framework provides a sound and insightful explanation of proton structure as expressed in DFs. The study highlights the importance of diquark correlations in the proton wave function and the role of Pauli blocking in explaining the asymmetry of antimatter in the proton. The results also show that the SCI predictions for the proton's DFs are consistent with modern data and other theoretical models. The study concludes that the SCI framework provides a robust and insightful explanation of proton structure as expressed in DFs.