Is a father obligated to provide his daughter with the same requirements for marriage that he provided his son, knowing that she completed her university education while the son voluntarily left his studies? And is it permissible for the father to withhold his daughter's wages if she works with him, based on the foregoing?

What your father spent on your brother for his marriage, in terms of expenses like housing (not ownership), does not obligate him to give the same to the rest of the children. However, what exceeded the need, such as owning an apartment, requires him to equalize among his children, either by giving the rest of his children the same as he gave the first, or by reclaiming what he gave to the first. As for gifting an apartment to the grandchild, there is no harm in it and no equalization is required for it. And it is permissible for the father to take payment for his son's work in exchange for college expenses, because university education expenses are not obligatory upon the father.