This post is a little old, but to offer a possible answer the question regarding the usage of the word "Rus", Sarmations were known as the Ras, Rosh, Rashu, and Rus and inhabited Rasapu which is now Southern Russia. Three theories I can offer are:
1. English translations of the Hebrew word "Rosh" as a noun meaning a place in Russia.
2. English translations of Greek reference text word "Rosh" as a adj meaning Price of Rosh
3. Unlikley, referenced to depict the fictional destruction of the Saxon army in a 'epic' version as described in the Bible's Ezekiel. Where the usage of 'Prince' of Rosh and the word Meshech (pernounced Mo-shok; current usage word Moscow) are combined Pirnce of Meshech as one of the nothern tribes in the future invasion of Israel.
I don't know that much about the writers, director, producer of the movie but I would venture to guess that "Rus" is a reference to the geographical origins of the Sarmations.