Is it permissible for me to complete my medical studies to help my Muslim sisters, despite my father's objection, as he does not wish for that? Would this be considered disobedience to parents (ʿuqūq al-wālidayn), and would I be sinful for it? And if my father agrees but does not like it, would this be considered disobedience?

If studying medicine does not involve forbidden matters and does not result in real harm to the father, then the father has no right to prevent you from it, and your disobedience to him is not considered an act of disrespect (uquq). However, if your father is greatly pained by your studies, then you must abandon them, unless this pain is due to foolishness or the like. It is advisable to discuss the matter calmly with the father to understand his point of view and try to convince him of the benefit of studying.