Heavy-haul trains play a crucial role in long-distance bulk transportation, yet their enormous mass and kilometer-scale length lead to complex longitudinal interactions and high coupler forces, which threaten operational safety. Conventional mechanism-based models, while accurate, are computationally expensive and unsuitable for real-time prediction. To address this limitation, this study develops a data-driven prediction framework that combines physics-based modelling and deep learning. A detailed longitudinal dynamics model of a 20,000-ton train operating on the Shuohuang Railway is constructed, incorporating traction, electrical braking, and resistance characteristics to compute coupler forces under varying gradients and curvature conditions. Based on this model, a QP-based optimization algorithm and a high-fidelity simulation platform are used to generate multi-strategy operating datasets that balance energy efficiency, punctuality, and ride comfort. The resulting data are processed using normalization and sliding-window segmentation to form supervised learning samples. A multi-resolution dual-stream LSTM (MRDS-LSTM) and its attention-enhanced variant (MRDS-LSTM–Attn) are then proposed to capture both short-term fluctuations and long-term temporal trends. Compared with RNN, GRU, LSTM, Bi-LSTM, NLSTM, CNN-LSTM, CNN-NLSTM, CapNet-NLSTM, Transformer, and Informer baselines, the proposed model achieves the highest prediction accuracy with MRDS-LSTM-Attn achieves an MAPE of 2.57%, and