Is it permissible to live off and benefit from the wealth of a father who does not maintain prayer, nor pay the obligatory zakat, but does give voluntary charity?

We advise you to continue counseling your father and not to despair of his guidance. There is no harm for you in eating his food and benefiting from his wealth. You must explain to him the seriousness of withholding zakat (definition), and that charity given without the intention of zakat does not suffice for the obligatory zakat. He must pay the zakat on his wealth for the past years.