Discrete time crystals (DTCs) have emerged as a novel non-equilibrium phenomenon, exhibiting spontaneous symmetry breaking of discrete time translation symmetry, and holding promise for applications ranging from enhancing quantum sensing to protecting quantum entanglement. Nevertheless, analytical quantification for disordered DTCs remains challenging, leaving uncertainties about their behaviors in large scale systems amid current debates on the stability of (Floquet-)many-body localization. In this work, we introduce an analytical framework to calculate the values of key observables in a strongly disordered DTC without fitting parameter. The perturbatively obtained closed-form formulae show quantitative agreement with numerical simulations for inverse participation ratios for eigenstate localization in Fock space, Edwards-Anderson parameters for spin-glass orders, mutual information for long-range entanglement, and the steady-state amplitudes of autocorrelators for period-doubled oscillations. Meanwhile, we demonstrate that eigenstate resonances render the scaling for the deviation of physical observables from their unperturbed values as $O(\lambda )$, in contrast to non-resonant situations with suppressed deviation $O({\lambda }^2)$. Our newly developed scheme adopts resolvent perturbation formalism, which can directly prescribe arbitrarily higher-order corrections without iterations. With such advantages, we analytically prove that quasienergy corrections for pairwise cat eigenstates are identical up to order $O({\lambda }^{(L/n_{\mathrm{\text{op}}})-1})$, where perturbations of strength $\lambda$ involve at most $n_{\mathrm{\text{op}}}$-spin terms. Such spectral pairing deviations quantify the DTC lifetime as ${\tau }_{*}\sim (1/\lambda {)}^{L/n_{\mathrm{\text{op}}}}$. We further show that the analytical framework applies to generic DTC models with dominant Ising interaction and a given number of qubits, offering a unified scheme to quantify physical observables for systems beyond numerically accessible sizes, with or without disorders.