While he does have a connection to all these, I could also see the following happen:
#3 will be tackled by Inosuke and Zenitsu, because they feel guilty about not having been of much help when fire-hashira died.
#1, the ancestor will be fought, but turned by talk-no-jutsu. Then he turns on Muzan and is killed by him.
Muzan is left, who Tanjiro fights, but not all by himself.
I dunno, how many upper demons are left? The other hashira need some activity, too, lol.
Maybe, although then the camera saved them, lol.I'm not actually sure his daughters got blown up. While his wife was with him as the explosion went off, when it cut back to where the girls were just before the explosion, they were already gone and the ball was just sitting there. So I'm thinking they might have left or been pulled away before the blast.