Per- and polyfluoroalkyl substances (PFAS) are persistent contaminants that are difficult to remove by conventional water treatment. Direct contact membrane distillation (DCMD) offers a promising alternative through vapor-phase transport, enabling high PFAS rejection and water recovery. However, membrane wetting at elevated temperatures and ionic strengths can compromise separation performance. To address these challenges, the main objectives of this study are to (i) develop a fluoropolymer (FP)-based surface modification to enhance membrane hydrophobicity and wetting resistance and evaluate PFAS chain-length effects (PFOA and PFBA), (ii) investigate the effects of temperature gradient (ΔT = 30-5oC) on PFAS rejection and flux stability, and (iii) assess the influence of feed ionic strength (2-50mS/cm) on DCMD performance. Surface modification increased the water contact angle from 118.5o to approximately 146.5o, indicating substantially enhanced surface hydrophobicity. Under single-solute conditions, pristine PTFE achieved ~99% PFOA rejection but showed lower rejection of short-chain PFBA (~93%), whereas FP-modified PTFE maintained ~99% rejection for both PFBA and PFOA. Increasing ΔT from 30 to 50°C reduced PFOA rejection by pristine PTFE from 82% to 63%, while the FP-modified membrane consistently maintained ~99% rejection across the investigated temperature range. Similarly, as feed conductivity increased from 2 to 50 mS/cm, PFOA rejection by pristine PTFE declined substantially from 82% to 34.5%, whereas FP-modified PTFE sustained ~99.5% rejection even at the highest ionic strength. Moreover, the FP-modified membrane maintained high water flux (~17-19 Lm-2h-1; J/J₀ > 0.9) throughout 24h of operation, demonstrating robust wetting resistance and stable separation performance under challenging operating conditions.