Shouldn’t the older Doc already know about his imminent death in 1885?
To backtrack, at the end of Back to the Future 2, when the older Doc from 1985 was sent back to 1885, Marty meets with the younger Doc from 1955. There, they see the gravestone of Doc who appears to have died in 1885 to Buford Tannen over a duel.
As I said previously, if the younger Doc in 1955 will end up growing to the older Doc who is sent back in 1885, shouldn’t the older Doc already know about his imminent death in 1885? For that, couldn't Doc have easily paid Buford Tannen off and call off the duel which will lead to his death?