What is the ruling on benefiting from a father’s money if its source is unlawful, and the son has no other source of livelihood? And is it permissible to take money from him to start a project, spend on oneself, or eat with him?

If the father's money is mixed (some of it unlawful and some lawful), there is no harm in benefiting from it for sustenance and borrowing, though it is disliked. However, if all of his money is unlawful, it is not permissible to benefit from it except out of necessity, and one must refrain from it when one becomes self-sufficient with lawful money. Some scholars have held the view that it is permissible to benefit from unlawful money due to its acquisition, not its essence. It is advisable to consult scholars for detailed clarification on the matter.