Is repentance for the obsessive thoughts of mocking religion permissible, regardless of whether the questioner has committed disbelief or not, especially since he has felt disbelief?

Do not pay attention to whispers [waswas]. You remain steadfast in Islam, and this foundation is not removed by mere doubt. Repentance is good and accepted if you are sincere. General repentance, where its owner resolves to be upright and shun what the Shariah has forbidden, erases all sins.