How can a woman deal with her ill-tempered husband who does not acknowledge his mistakes, and are there specific adhkar to improve his disposition?

There are no specific adhkar (remembrances of God) for improving people's dispositions. However, there are virtuous qualities and noble morals that a wife can embody to improve her husband's disposition, including: improving her connection with Allah, responding to evil with good – "Repel evil with that which is better" [Qur’an 23:96] – patience, cheerfulness, being a good wife, and overlooking mistakes. It is also recommended to supplicate for him, persist in these virtues, not despair, and seek reward from Allah, while knowing that married life is not devoid of difficulties.