Is the brother's failure to purchase the state land that the deceased father left behind, which caused the father to be seen naked in a dream, the reason for his torment and accountability for it?

There is no need to seek permission from the ruler to revive dead land, due to the generality of the Prophet’s (peace be upon him) saying: “Whoever revives dead land, it belongs to him.” An exception to this is if the inhabitants are harmed by the revival. Based on this, there is no blame upon you or your father in owning this land as long as it does not cause harm to anyone. Be aware that legal rulings are not based on dreams.