1-I dont remenber that dialogue very well soo imma just not comment on it, but after that Luffy and Zoro stayed in Wano for some time, specialy since Luffy was in prison for who knows how long, a week or soo at least, then they spent 1 more week training. Its very likely they are at the end of that month now.
2-Most of that plot was soo that the flying six got separated to search for yamato, and it also had some importance in teasing X-Drake betrayal while making us think Whos who and Queen wanted to kill each other.
3-Thats just what Kaido wants, its like saying Robin should have crossed the gate in ennies lobby just because what lies beyond the gate was teased.
4-The saccabards are still alive..And according to mithology its Yamato that kills Orochi, he might still show up and atack Momo.
5- Why does he need to have it? he already has Emna.