Is what happened to the speaker—of believing a whisper that says, "There is no interpretation for the seemingly contradictory hadiths of the Prophet"—considered apostasy from Islam? And is his intention not to pray 'Isha considered apostasy that necessitates redoing the prayer? And is his repeated utterance of the Shahadatayn with the intention of entering Islam valid, or should he disregard these whispers?

O noble questioner, you are afflicted with waswasah (obsessive whispering). This thought that occurred to you does not nullify your Islam, nor was it necessary for you to repeat the 'Isha prayer. Rather, all of this is satanic waswasah, and you must disregard it. The default is the preservation of one's Islam, and it is not removed except by certain knowledge of having committed one of its nullifiers. Mere self-talk does not cause one to abandon the religion, as long as the servant dislikes these whisperings. Uttering the two shahadas (declarations of faith) is a good deed, so adhere to this blessed remembrance while firmly believing that you are a Muslim. Cast away these whisperings from yourself and strive to acquire religious knowledge.