Why do your answers differ regarding the number of the Prophet's صلى الله عليه وسلم wet nurses, with one fatwa mentioning four, another two, and a third three, and what is the most authoritative opinion with evidence?

There is no contradiction between the fatwas. Fatwa No. 52382 clarifies who first suckled the Prophet (peace be upon him), and Fatwa No. 71541 mentions his wet nurses based on available information. As for Fatwa No. 67554, it is closer to research and aligns with what Ibn al-Qayyim mentioned in "Zad al-Ma'ad" regarding the mothers who suckled him.

The Prophet's (peace be upon him) wet nurses were: 1. Thuwaybah, the freed slave of Abu Lahab: She suckled him for a few days, and also suckled Abu Salamah and Hamzah with him. 2. Halimah al-Sa'diyah: She suckled him with the milk of her son Abdullah, and also suckled his cousin Abu Sufyan ibn al-Harith with him. 3. A woman from Banu Sa'd: Other than Halimah, she was a wet nurse for Hamzah, and she suckled the Prophet (peace be upon him) for a day while she was with Halimah. Thus, Hamzah was suckled by the Prophet (peace be upon him) both by Thuwaybah and by this Sa'diyah woman.