Reciting Al-Fatihah is required in Every Rak'ah of the Prayer
The fact that Fatiha is required in each Rakah is something all scholar agree on and is validated from the following hadith:
"Whoever performs any prayer in which he did not recite Umm Al-Qur'an, his prayer is incomplete"(Ahmad 2:250). There are similar hadith narrated in Fath Al-Bari 2:276 and Muslim 1:295.
Tafsir of Isti'adhah (seeking Refuge)
The remedy to Shaitan's whispers are detailed in Surah Al-Araf (199-200), Surah Al-Muminun (96-98), and Surah Fussilat (34-36) where Isti'adhah is prescribed. The relentless nature of Shaitan is such (due to his enmity with Adam and his progeny) that even his whispers can be dangerous. The nature of Shaitan's hatred of mankind is detailed in Surah Al-Araf (27) and Surah Fatir (6) and these two ayaat are interesting foils that accomplish the same message. In Surah Al-Araf, ayah 27, we are warned of the apparent and well known consequences of Shaitan's deceptions, getting Adam and Hawwa thrown out of Paradise. In Surah Fatir, ayah 6, his invitations have little to do with Paradise, but are only a gateway to "become the dwellers of the blazing Fire".