What is the ruling on repeating verses of Al-Fatiha for fear of forgetting a word, and do sexual fantasies or a feeling of coldness and shivering and the emission of a moist substance while washing the urethral opening affect the validity of the fast?

You must recite Al-Fatiha, and there is no weight to the feeling that some words are omitted, as it is a [form of] waswasa (whispering from Satan), and its cure is to disregard it. As for doubting the emission of something wet, it does not remove the certainty that nothing was emitted, and there is no need to inspect. Therefore, your fasting is valid. It is recommended to supplicate and consult a psychiatrist.