Is it permissible to make up for only two days' worth of missed prayers, out of all the missed prayers, or is it obligatory to do more than that?

The whispers (waswas) have reached a significant level, and you must be cautious not to give in to them, as they lead to great evil. You are not required to make up prayers that you doubted after completing them, because doubt at that point does not affect the validity of the worship. If you prayed with a small amount of menstrual blood on your clothes, this does not affect the validity of the prayer, because a small amount of blood is excused. Similarly, if someone prayed while unknowingly having impurity on them, their prayer is valid and they are not required to repeat it. There is no sin upon you if you did not sleep in the described situation.