What are a mother's rights over her son, and to what extent is sending her money sufficient without communicating with her, especially if the father did not show piety due to his injustice?

The believer, when called to Allah and His Messenger, is obligated to say, "We hear and we obey." He has no choice when Allah and His Messenger have decreed a matter. Parents have a great right that is not nullified by their disobedience or disbelief. One must accompany them in this world with kindness and try to advise them and call them to Allah. The son should advise his father that cursing the religion is major disbelief, and advise his parents against the permissibility of their relationship if a triple divorce has occurred. He must honor and maintain ties with them in every possible way, and beware of abandoning or cutting them off, as that is among the gravest sins.