What is the religious ruling on shunning an abusive father to avoid falling into sin, and what are the religious implications of such an action?

It is obligatory to be dutiful to one's parents and treat them with excellence, even if they are harsh in their dealings. It is not permissible to abandon them or refuse to speak to them. Rather, it is obligatory to maintain ties with them and be careful not to provoke them. One can avoid sitting with them if it incites their anger. Enduring their ill-treatment and showing them kindness may be an expiation for sins, along with supplicating for their righteousness and seeking assistance from wise relatives or friends to influence them.