[OwdBKKHO]

does the Quran not refer to the believing Christian and the believing Jew and the believing Sabian ?

Does the Quran not say no one is accountable till they recieve the message. ?

Is unitarianism not an inclination towards monotheism ?

Is Islam not monotheism ?

Given the lack of access to Islamic material, or any muslims, and the threat of a excommunication or heresy, i think he deserves a Mashallah ?

You mean this verse?

Indeed, those who believed and those who were Jews or Christians or Sabeans - those [among them] who believed in Allah and the Last Day and did righteousness - will have their reward with their Lord, and no fear will there be concerning them, nor will they grieve.

This is talking about the Jews, Christians and Sabeans that came before Prophet Muhammad. As in, the real Christians, who followed Isa's teaches, and the real Jews, who followed Moses' teachings.
But I'll let Brother amr123 post the full tafseer of this ayah, inshaAllah.

Yes, the core of Islam is monotheism, but Newton did not accept many key aspects of Islam, like the Prophethood of Muhmmad , and this makes him a non-Muslim. Not all Monotheists are Muslims. Jews and Sikhs are monotheists, are the Muslim? No.