What is the ruling of Islamic law regarding money from an illegitimate source, and how can one atone for benefiting from this money? Is Hajj accepted with the presence of this money, and how can this debt be repaid?

Firstly: It is not permissible to defraud the state to obtain money and aid, as this involves lying and consuming wealth unjustly. Sin attaches to the perpetrator and to whoever incited them to the act. There is no sin upon you due to your young age and your disapproval of your parents' actions. You must be cautious and refrain from taking any of this money. If your father has lawful money mixed with this money, it is permissible for you to eat from his food when in need.

Secondly: You are not obligated to return the government's money, but you must advise your parents to stop taking it. What they took before knowing it was forbidden incurs no sin upon them. As for what was taken after knowing it was forbidden, if they cannot return it to the state, they must dispose of it by giving it to the poor and needy.