What is the ruling on the unintentional emission of semen at night after reading sexually stimulating material, and is it permissible to adopt the view of other schools of thought regarding the non-invalidation of the fast if the majority of the country's inhabitants are Maliki?

If semen is discharged at night due to thinking, there is nothing upon you. However, if it is discharged during the day, your fast is valid according to most scholars, and you are not required to make up for it or offer expiation. The Maliki school has a detailed explanation regarding this: If you persist in thinking and discharge semen, then expiation is required if it is your habit to discharge semen from persistent thinking. However, if it contradicts your habit and you discharge semen, there are two opinions regarding expiation, and the preferred opinion is that no expiation is required. The view of the majority of scholars is that expiation is only obligatory for intentional sexual intercourse during the daytime in Ramadan. You are permitted to follow the opinion of the majority of scholars, and you are not obligated to adhere to a specific school of thought. You must repent to Allah Almighty if that fiancée was not lawfully contracted to you, as she is a non-mahram, and it is not permissible to converse with her with words that contain doubt, for sins are magnified during virtuous times like Ramadan.