Accurately modeling gas–surface interactions during atmospheric re-entry is essential for designing ablative thermal protection materials. This work presents a new calibration of reaction rates in the finite-rate Air–Carbon Ablation (ACA) model of Prata et al., using expanded high-pressure Plasmatron measurements together with low-pressure molecular beam data. Experimental uncertainties are explicitly included, and Bayesian inference is accelerated through surrogate modeling. We first calibrate the atomic nitrogen reaction subset and obtain a finite-rate nitrogen model validated across both low- and high-pressure conditions. We then extend the calibration to atomic oxygen reaction rates using combined low- and high-pressure oxygen observations. The resulting calibrated models improve predictive capability compared with the baseline ACA and provide a more robust, uncertainty-aware basis for gas–surface interaction modeling in atmospheric re-entry design.