What is the way to deal with recurring whispers and doubts about the Oneness of Allah and Tawhid, and can I be guided to decisive proofs in this regard?

We congratulate the questioner on her steadfastness and her eagerness to perform acts of worship. The whispers that she experiences regarding ablution, prayer, and creed are most likely from the cunning of Satan. She must repel these whispers and seek refuge in Allah from the accursed Satan, for certainty is not removed by doubt. The oneness of Allah does not require proof, and its proofs are too well-known to be mentioned. A collection of proofs for Allah's existence and oneness has been mentioned in Fatwa no. 41450. Additionally, Sheikh Muhammad ibn Ibrahim Al ash-Sheikh has a treatise on faith in Allah, included among his رسائل (epistles), in which he explained the proofs for Allah's oneness from the perspectives of innate disposition (fitra), revealed law (Sharia), intellect (aql), sensory experience (hiss), and the indication of His names and attributes.