This paper (v2.0) presents the corrected and definitive formulation of the Matrix Identity Field (MIF) theory, a unified framework designed to resolve major persistent problems in modern physics and cosmology. This version replaces a previous manuscript that contained a dimensional inconsistency in a key derivation. The MIF theory posits that physical reality, including spacetime and all fundamental interactions, emerges from the dynamics of a single, fundamental, matrix-valued field. The theory is built upon one non-arbitrary parameter: a vacuum mass scale, m₀ ≈ 70 MeV/c², which is derived from the electron mass and the fine-structure constant. A central success presented in this revised work is the first-principles derivation of the MOND acceleration constant, a₀. We prove that a₀ is not a free parameter but is a direct prediction of the theory, emerging from the relationship between the MIF mass scale m₀, the Planck scale, and a geometric factor of 1/3. The predicted value is in excellent agreement with observation. The paper summarizes the core postulates of the theory and confronts its predictions with a wide range of experimental data, from particle masses (W/Z bosons, proton, muon) to cosmological phenomena. We demonstrate the theory's viability as a candidate for a grand unified theory and honestly assess its current successes and areas requiring further refinement, such as the prediction of the vacuum energy density.