All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallAllahu 'alayhi wa sallam, is His Slave and Messenger.
It is quite clear that you are suffering from Waswasah (obsessive whisperings). We advise you to ward off these devilish whisperings and disregard them entirely and never pay attention to them. In principle, you have not committed any act of disbelief taking you out of the fold of Islam – Allaah forbid - unless proven otherwise.
Therefore, you should repel such bad thoughts and devilish whisperings. It suffices that you to turn to Allaah in repentance; repent from all your past sins and misdeeds and resolve never to commit them ever again and to adhere to the straight path, abide by the religious obligations, and avoid all that is forbidden. This is sufficient for you: to repent from any sin you may have committed whether you know it or not.
For more benefit, please refer to Fataawa 23074 and 86527.
Regarding reciting an Ayah (verse) from the Quran while doubting the correctness of its wording, this is impermissible. Instead, you have to verify the wording of what you are reciting and to make sure that it is correct.
Allaah knows best.