What is the "end of the saddle" mentioned in the Hadith, and is what invalidates the prayer limited to the black dog, the woman, and the donkey, or does the passing of a man also include?

The "akhirat ar-rahl" (end of the saddle/pack) is the piece of wood located behind the rider on a mount. It is the minimum length for a sutrah (barrier), approximately two-thirds of a cubit. The prayer is not invalidated by the passing of a woman, a dog, or a donkey. The majority of scholars interpreted "cutting off the prayer" in this context as a reduction in reward due to the heart being distracted.