The name Octavian is incorrect, and should be Gaius Octavius instead. In Latin the suffix '-ianus' indicates the original family name after an adoption, as a result of which the adoptive son received the full name of the adoptive father. Accordingly, C. Octavius changed his name to C. Iulius Caesar Octavianus after being adopted and made sole heir in his grand uncle's will (44 BC). As a matter of fact, the future emperor did not like and never himself used the epithet Octavianus pointing at his not being born a patrician.
The Roman cavalry has stirrups, which were not used by the Romans. Stirrups were introduced in Europe in the 7th and 8th centuries.
Marc Antony's legion was the 3rd not the 13th.