What is the ruling on dependence (tawākul), and what is the Islamic legal perspective on it, especially if a person is capable of fulfilling their duties but refuses to do so and exploits others?

What your brother is doing, hanging his needs on you without necessity, is blameworthy in Islamic law and naturally reprehensible. This is because Islam has encouraged self-restraint and independence from people, and has forbidden begging without necessity. The Prophet, peace and blessings be upon him, said: "Indeed, begging is not permissible except for three: for one in dire poverty, or for one burdened by heavy debt, or for one with a painful injury." And the saying of Gabriel, peace be upon him, to the Prophet, peace and blessings be upon him: "And know that the honor of a believer is in observing night prayers, and his glory is in his independence from people."

As for his boycotting you because you refused to comply with his demands, this is impermissible, as it is not lawful for a Muslim to boycott his Muslim brother without a legitimate legal reason. This is even more strictly forbidden when it involves kin. We advise your brother to fear Allah, and we guide you to counsel him gently and kindly, hoping that Allah will guide him.