Rod Hallett who plays Benedict Arnold previously had played another man that has gone down in history as a turncoat of sorts. He played Sir Richard Rich on The Tudors. He was a lawyer and Lord Chancellor of England during the reign of Henry VIII who helped convict people who he had been friendly with such as Thomas More.
In the show Jamie's hand is injured during the battle. Other than a cut down the middle it does not seem to be too bad. In the book his hand is seriously injured causing Claire to call it hamburger and forcing her to amputate his ring finger that had been previously damaged thanks to Black Jack at Wentworth.
The actors playing Major General Gates and Simon Fraser are 20 and 17 years older than Sam Heughan who plays Jamie. Jamie would have been 6 and 8 years older than them in real life since Jamie was born in 1721 while the real life Gates was born in 1727 and Simon Fraser in 1729.