Is it permissible for a son who is psychologically incapacitated and suffers from social phobia to be financially supported by his parents, and what are the limits of this support, and what is he entitled to ask of them in terms of treatment, education, and food?

A father must provide for his child who is unable to earn a living. This provision must be reasonable (bi'l-ma'ruf) to cover the child's food, drink, clothing, and medical treatment without extravagance. This is based on the Prophet's (peace be upon him) statement to Hind bint Utbah: "Take what suffices you and your child, according to what is reasonable." As for educational expenses, they are not part of the obligatory maintenance.