Short answers, pulled from the story.
Marcus Terentius Varro was born in or near Reate, now known as Rieti in the Lazio region of Italy. He owned a large farm in the Reatine plain located near Lago di Ripasottile until his old age.
Marcus Terentius Varro reached the office of praetor while supporting Pompey during the turbulent years leading up to the First Triumvirate. The formation of that coalition in 60 BC likely cost Varro any chance of rising to consulship.
Six books out of twenty-five survive from this massive work though they remain partly mutilated by time. The oldest existing manuscript is Codex Parisinus 6842 written in Italy before the end of the 12th century.
Marcus Terentius Varro warned readers to avoid swamps and marshland because certain minute creatures bred there could not be seen by human eyes. These invisible organisms floated in the air and entered bodies through mouth and nose causing serious diseases.
Julius Caesar appointed Varro to oversee the public library of Rome in 47 BC placing him in charge of preserving knowledge for the state. Following Caesar's death Mark Antony proscribed Varro resulting in significant property loss including his entire library.