Nice to see you back. It is not possible for me to agree with all your assumptions. Your bias against the Arabs has always crossed all bounds, so much so that you are bent upon denying the existence of the Prophet Muhammad (S) as a particular person who ever existed.
... Oh one more thing : there is no Muhammad either. Check Surah 47 (Surah AL Muhammad ! !) for yourself. The Quran uses the words muhammadun and muhammadin which are adjectives - meaning a 'praiseworthy person'. So in the Quran, the name of the Prophet is not Muhammad. ...
Surah Muhammad is Surah Muhammad.
Many names are nouns as well as adjectives. Look at your own name SAIM.
Muhammad = Praised one.
Muhammadin, Muhammadun = Muhammad is.
Without the real existence of a particular person, the exalted Prophet Muhammad (S) who received and conveyed to us Allah's message in Arabic, there can be no Islam.
Another note: I agree with your last understanding of SAUM. Can you please post your translation of 2:183-187?
Thanks & best regards