Background: The SADA framework (Bust, 2026a) proposes that Earned Secure attachment is a dynamic metabolic state subject to quantifiable erosion. The Superposition-Collapse Model (Bust, 2026b) demonstrates that this erosion produces attentional dysregulation indistinguishable from ADHD on behavioral checklists. Both models require an empirically grounded measurement protocol to operationalize their predictions and enable clinical application. Objective: This paper introduces the SADA-Entropy Protocol, a composite biomarker framework that quantifies the biological integrity of the attachment regulation system through four weighted measurement domains. The protocol is designed to (1) detect SADA onset before subjective awareness, (2) differentiate SADA from primary psychiatric diagnoses, (3) guide intervention sequencing based on domain-specific failure patterns, and (4) provide longitudinal tracking of treatment efficacy. Methods: The protocol integrates four validated measurement approaches into a single composite score (0–100): Domain 1 — Autonomic Entropy via Refined Composite Multiscale Entropy of heart rate variability (RCMSE; 35% weight); Domain 2 — Neuroendocrine Dynamics via Cortisol Awakening Response kinetics (AUCg/AUCi; 25% weight); Domain 3 — Sleep Architecture Integrity via NREM N3 percentage and fragmentation index (25% weight); Domain 4 — Interoceptive Fidelity via heartbeat detection accuracy and the accuracy–sensibility gap (15% weight). Data collection requires a 72-hour continuous monitoring period with concurrent salivary cortisol sampling and interoceptive assessment. Results: The composite score classifies individuals into three zones: Earned Secure (80–100), Limbic Friction (50–79), and SADA Onset (0–49). Each zone has specific threshold values across all four domains. The protocol maps domain-specific failure patterns onto the three SADA routes identified in Paper 1 (from Earned Secure, Anxious, or Avoidant starting points), enabling targeted intervention selection. Preliminary clinical observation suggests that RCMSE decline precedes subjective awareness of burnout by 2–6 weeks, providing a predictive window for early intervention. Conclusions: The SADA-Entropy Protocol transforms the theoretical propositions of the SADA framework into an empirically testable and clinically actionable assessment system. By measuring the structural complexity of autonomic output rather than its magnitude, the protocol captures what standard HRV metrics miss: the progressive decomplexification that constitutes the biological signature of attachment regulation failure. The protocol is proposed for prospective validation in clinical populations.