The integration of Internet of Things (IoT) devices with blockchain technology offer enhanced data security, traceability, and decentralization. However, IoT devices face challenges such as limited computational power, energy constraints, and fluctuating network conditions, which make robust cryptographic implementation difficult. Digital signatures, which are essential for data integrity and authenticity in distributed blockchain systems, must be adapted to these constraints. While the Edwards-curve Digital Signature Algorithm (EdDSA) is secure and efficient, its static threshold implementations do not suit IoT networks, where rigid thresholds can cause excessive computational overhead or reduced security. Our work introduces a Dynamic Threshold EdDSA (DT-EdDSA) that adjusts signature thresholds in real time based on transaction priority, device capacity, and network conditions. By dynamically adapting the cryptographic intensity, DT-EdDSA reduces the computational and energy overhead on resource-limited devices while maintaining strong security during critical operations. Simulations show that DT-EdDSA significantly improves energy efficiency, signature generation time, and security resilience compared with static models, addressing IoT security limitations. This approach provides a flexible, context-aware cryptographic solution for IoT-blockchain networks, underscoring the relevance of adaptive techniques in meeting the security challenges of decentralized IoT environments.