Pullo is talking about "smoking all the smoke" in Rome, but he is not talking about tobacco. Tobacco was native to North America. The Ancient Romans smoked opium, which was imported from Egypt.
When Caesar is listening to the troop-status reports, the officer in charge mentions that some of the soldiers have died from "flux". Flux is a term used to describe dysentery or other diseases causing the loss of fluid by diarrhea or hemorrhage. Dysentery and illness in general was the largest causes of death for soldiers in the field up until the modern era. More soldiers in world-history have died from illnesses in the field than from combat related wounds.
Mark Antony's public appeal as shown here is historically accurate. Historians say that Antony was the superstar of his day. He is also correctly portrayed as rather vulgar, despite being of noble birth.
The Rubicon River has changed so many times due to flooding and seasonal runoff that its location in Caesar's time cannot be accurately placed.
The Rubicon River was the dividing line between Gaul and Italy. Under Roman law, no army could enter Italy under arms. To do so was treasonous. Simply by leading his army across the river Caesar was declaring himself an outlaw.