“I wonder if his James Otis is a descendant of the James Otis of Boston Revolutionary days”
Could be. That James Otis was son of James, and had a son named James. One more generation would land in about the right time.
Then there is this: “Otis died suddenly in May 1783 at the age of 58, as he stood in the doorway of a friend’s house, when he was struck by lightning.”
https://en.wikipedia.org/wiki/James_Otis_Jr.
Otis suffered from increasingly erratic behavior as the 1760s progressed. He received a gash on the head by British tax collector John Robinson's cudgel at the British Coffee House in 1769. Some mistakenly attribute Otis's mental illness to this event alone, but John Adams, Thomas Hutchinson, and many others mention his mental illness well before 1769. The blow to the head was not the cause of Otis' mental illness, but it made it far worse and, shortly after, he could no longer continue his work. By the end of the decade, Otis's public life largely came to an end, though he was able to do occasional legal practice during times of clarity.This James Otis is the one in "Johnny Tremain," where his dementia is attributed to the head injury.
A couple more generations of Jameses would bring us to George Strong's time.