What is the way to deal with the continuous whispers of Satan, which affect the recitation of the Quran and acts of worship with strange thoughts, despite frequent seeking of refuge (with Allah) and supplication, and should one fear that their deeds and acts of worship might be rendered vain because of them?

You have done well by resorting to Allah through supplication and seeking refuge in Him. You must turn away from the whispers (waswas) and preoccupy your heart from them, and increase in the remembrance of Allah and recitation of the Qur’an. The beneficial cure for waswas is to completely ignore them. If they are not paid attention to, they will disappear after a short while. But if one listens to them, they will increase. It has been reported that whoever is afflicted with waswas should seek refuge in Allah and desist. Its cure is also to believe that it is a satanic thought and to fight it, for one will be rewarded like a mujahid (one who strives in Allah's cause). It is also recommended for one afflicted with it during ablution or prayer to say: "La ilaha illa Allah (There is no god but Allah)," for Satan shrinks back upon hearing it.