I'll be honest with you. Very few Coptic movies I like, and those that I do like seem to be on the more contemporary saints, and even then, not great. Copts tend to over-dramatize and exaggerate. So I wasn't very keen of the movie when I saw this. With that said, I'm pretty sure the sources might be from Coptic and Copto-Arabic sources:https://www.gorgiaspress.com/bookshop/pc-57432-87-the-life-and-works-of-severus-of-antioch-in-the-coptic-and-copto-arabic-traditionbrby-youhanna-youssefbrgorgias-eastern-christian-studies-28.aspx
That's my guess (ridiculously expensive, I know). There are also some pdf's by this author lurking online that I haven't read either.
My specific criticisms of the movie:
---St. Severus strikes me as a strong personality you don't mess with with a spiritual side. Forgive me for saying this, but the actor is a "softy". He would probably be great for other saints with that type of reputation, but I imagined St. Severus not to be that type of personality in the movie.
---The emperors, including Anastasius, seem to be portrayed as "crazies". Yes, Anastasius was on our side, but even the actor for him made him to be this mentally unstable character. And Justinian was much more intelligent than the movie made him out to be. Being as someone who knows history in detail, the hagiographical portrayal is very off-setting. Justinian did have a council with supporters of St. Severus openly debating the supporters of Chalcedon. Justinian struck me as a personality who is torn between supporting Chalcedon and also somewhat seeing St. Severus' point of view when looking deep in history. That is not to say he had his evil side as well in persecuting us, but I respect a movie more if they can show a complicated character, not a cartoon character as this movie did.
---They left off other aspects of St. Severus' life. His connection with St. Peter of Iberia, his joining of the Acephali, his dealings with specific heretics even in our own Church, not just outside the non-Chalcedonian Church. And I'm not surprised the movie does not show his issues with St. Peter III. How can the movie explain a Coptic Pope who staggers and being questioned by St. Severus? No, our Popes are "always perfect" in the movies. The mentality has not changed.
Now, here is what the movie did well in:
---It showed the ambiguity of his family past. The director used creative license not to show whether his family were Christians or pagans, but just a loving family wanting the best for their progeny to be educated well. The conversion story and baptism of St. Severus though needed improvement on the acting side.
---I appreciated the ambiguous end of St. Philoxenus as well, showing him tortured in the last scene for him, since we also have similar ambiguities in the history.
---The scene of St. Severus and the miracle of the reappearing prosphora was done very well. That one actually did give me some goosebumps, and I do like the story.
Other than that, I don't think I can answer some of your other questions. Perhaps Isa can answer your ancient geography question. And I'm guessing if there was a debate between St. Severus and Archbishop Macedonius, I would imagine a more intelligent discussion on both sides.
My two cents.