Must I return the excess money I took from my father over past years, knowing that he used to equalize monthly allowances between me and my brother, and I believe that the female gets half of what the male gets? And must I inform him of this opinion of mine so that he may differentiate between us in expenditure?

There is no obligation to return anything. The view of the majority of scholars regarding gifts to children is to equalize between males and females, based on the saying of the Prophet, peace and blessings be upon him: "Be equitable among your children in giving gifts. If I were to prefer anyone, I would have preferred women." This expenditure is considered maintenance (nafaqa), not a gift (hiba), and maintenance is determined by need.