Is the intention sufficient to ward off punishment from a husband who does not treat his wives justly, and what about my suffering due to his injustice towards me?

Justice must be observed between wives, and injustice is a sin that necessitates actual repentance, not just intention. Punishment is not definitively decreed for a specific individual except by a text, and the threat of punishment may not materialize due to reasons such as repentance or effacing good deeds. It is advised to be patient with the husband, occupy oneself with obedience to Allah, and supplicate for his righteousness, for piety towards Allah provides a way out for a person, and distress and harm elevate one's ranks and expiate sins.