Is a person considered disobedient to his father if he talks back to him while he is assaulting the mother or raising his voice at the children, especially if the father does not fulfill his responsibilities and is a source of domestic violence, despite suffering from epilepsy?

If the father's harmful actions are due to epilepsy, then he is not accountable, because he is not held responsible (mukallaf), according to the words of Allah Almighty: ﴿And there is no blame upon you for that in which you have erred, but [only for] what your hearts intended﴾, and the Hadith (definition): "Indeed, Allah has pardoned for my Ummah their mistakes, their forgetfulness, and what they are coerced into." However, if he does so by his own choice, then he is committing a wrong, as his actions contradict the enjoined good companionship, as in the words of Allah Almighty: ﴿And live with them in kindness﴾, and the Hadith: "The best of you is the best to his family."

Your response to your father, if it is an admonition delivered respectfully and without raising your voice, is permissible. However, if any verbal or physical abuse—no matter how slight—emanates from you, then it is disobedience ( 'uqūq), because Allah has forbidden merely showing annoyance, as Allah Almighty said: ﴿So do not say to them [even] 'uff,' and do not repel them but speak to them a noble word.﴾ Disobedience to parents ( 'uqūq al-wālidayn) is harming them in any way, whether little or much, or disobeying them in what they command or forbid, provided it does not involve disobedience [to Allah]. Your distancing yourself from him is not considered disobedience if it is not a complete severing of ties and does not harm him, especially if you are thereby safeguarding yourself from potential harm from him. Strive to show him kindness and do good to him, and pray for his well-being, for he has the right to be treated with kindness, even if he acts wrongly.