Abstract: To address the issues of multi-source stress superposition, the complex evolution of coal pillar load-bearing conditions, and the lack of a basis for determining backfill parameters during the exposure of clusters of parallel abandoned drifts in fully-mechanized top-coal caving faces in extra-thick coal seams, this study takes the discontinuous load-bearing zone formed by nine parallel abandoned drifts in front of the 13204 fully-mechanized top-coal caving face at Chejiazhuang Coal Mine as its engineering context. Using a combination of field surveys, numerical simulations, theoretical analysis, backfill mechanical tests, and on-site mine pressure monitoring, the stress migration patterns in discontinuous load-bearing zones, methods for identifying the instability of gradually thinning coal pillars, and the control mechanisms of complete backfilling were investigated. The results indicate that the discontinuous bearing zone formed by the cluster of parallel abandoned roadways consists of the abandoned roadways, the coal pillars clamped between them, and the damaged roof. A multi-peak high-stress concentration structure has formed on both sides of the pre-mining roadways and at the edges of the coal pillars between them, with vertical stress peaks of approximately 7.6–7.7 MPa and a stress concentration factor of approximately 1.43–1.45. During the advance of the working face, the pressure from the advance support gradually migrates toward the discontinuous bearing zone and superimposes with the lateral support pressure from the group of abandoned drifts; the stress evolution in the surrounding rock exhibits phased characteristics of “independent disturbance-stress superposition-peak bearing capacity-load transfer upon instability”. Based on the connectivity of the stress influence zone, the loss of effective bearing width, and the patterns of change in the load-dominant direction, a method for identifying the stages of gradual coal pillar instability was established. It is proposed to use the stress influence zone overlap coefficient, the effective bearing width loss rate, and the stress center of gravity shift coefficient to characterize the evolution of the bearing state of the gradual coal pillar. Under the existing discrete simulation conditions of the 13204 working face, 49, 6, 4 m correspond to the stress superposition initiation, peak load-bearing critical point, and buckling load transfer states, respectively. Full backfilling transforms the weakly constrained boundary of the empty drift into a load-bearing boundary, restructuring the original “empty drift pressure relief-concentrated load-bearing by coal pillars-intermittent roof support” configuration into a synergistic load-bearing structure characterized by “load compensation by backfill-lateral clamping by coal pillars-continuous basic roof support”. Local basic roof stability analysis indicates that the equivalent support strength of the backfill required to maintain the stability of a key rock block above a single empty drift is 1.96 MPa; Further analysis, incorporating the overall load-bearing behavior of discontinuous load-bearing zones, backfill strength tests, and the stress-strain response patterns of the surrounding rock under different backfill strength conditions, determined that a cement-fly ash backfill with a water-to-cementitious material mass ratio of 1∶1 and a 28 d compressive strength of 2.23 MPa represents reasonable backfill parameters. Field application has shown that after complete backfilling using these parameters, the 13204 fully-mechanized top-coal caving face safely exposed nine parallel goads without any roof falls or support collapse incidents, and mine pressure was found to be generally controllable.