Bottom line, black bears are easy to kill with a good clean shot, but tough to kill if you start a fight with a bad shot. Trouble is, if the fight starts you're standing there with an empty gun.
I'd have complete faith in your setup and no changes. I'd make sure of the shot, but in the meantime be working on your strategy for "what if."
It's kinda entertaining to read Lewis and Clark accounts of their many bear kills. Pretty good descriptions of loading on the run and lotsa running, tree climbing, and multiple shooters.
In your shoes, I'd be working on marksmanship, studying bear anotomy, practicing my speed loading, and probably loading on the move. I'd also get brushed up on my tree climbing, if L&C are fair teachers.
As for backup, I'd be thinking about it if it's legal in your woods. We tend to pack modern high power revolvers up here, but that might not be legal for you. Might be worth having a friend with a legal firearm or packing a period handgun if you prefer to hunt alone. I've been giving serious thought to one of
these or the flint version. I'd say it would do a real good job of finishing a fight when your rifle is empty.