Will God hold us accountable for hating our disobedient father who caused us psychological and physical suffering, even though we treat him with respect? And are we sinful for unknowingly cursing him in his absence?

Your father - may Allah forgive him - committed forbidden acts by neglecting your rights. However, it is not permissible for you to respond to this by mistreating him. For the father has a right to dutifulness and maintaining ties from his child, a right that nothing abrogates. You are not required to demand his heartfelt love, but rather to treat him kindly outwardly and to avoid mistreating him, whether he is present or absent. Cursing and reviling him are among the gravest of major sins, according to the Prophet, peace and blessings be upon him, who said: "Indeed, among the greatest major sins is for a man to curse his parents." One form of this is for a man to curse another man's father, which then causes the other man to curse his own father. Belittling him by mentioning his faults and shortcomings is backbiting (gheebah), which is forbidden, and it is even more strictly forbidden when done against a parent.