What is the optimal way to deal with satanic whispers that call to disbelief, and that haunt me during sleep and prayer, and return after ruqyah, knowing that I adhere to the Quran and acts of worship?

What you are experiencing is from Satan, and Allah does not hold a servant accountable for what passes through their mind unless they speak or act upon it, as the Prophet (peace be upon him) said: "Indeed, Allah has forgiven my Ummah for whatever evil thoughts cross their minds, as long as they do not act upon them or speak about them."

To overcome this, follow the guidance of the Prophet (peace be upon him) by sleeping in a state of purity and maintaining the remembrances before sleep, such as the Mu'awwidhat (Surahs Al-Falaq and An-Nas) and Ayatul Kursi. In prayer, seek refuge with Allah from Satan and spit lightly to your left three times if you feel the whispers of Khanzab, as it is confirmed that this dispels his whispers.

You must strive against these whispers and continue with legal ruqyah (exorcism) and fortify yourself with general remembrances, especially the morning and evening adhkar, the adhkar for entering and leaving the home, and those after the prayers. Read the last two verses of Surat Al-Baqarah at night, for they suffice against the need for night prayer, against Satan, and against misfortunes.

Increase your recitation of "There is no god but Allah alone, without partner; to Him belongs all sovereignty and all praise, and He is over all things competent" a hundred times a day; for it is a protection from Satan. Hold fast to Allah, rely upon Him, and seek refuge with Him from the accursed Satan.