To be perfectly honest, I think Oda could've resolved all of those above since long ago. But this is Jump we're talking about. So of course they would've made Oda drag it out as much as he can, i.e: milking the series for all its worth. Even the current Dressrosa arc is problematic.
Mashima also has a similar pacing to his series (pre-GMG), but with Mashima, I feel that he knows the right timing to lay down all the cards for us all to see. I'll be honest, I was close to dropping the series around GMG, but I'm glad I stuck through the Tartaros arc. And boy! was the pay-off worth it.....
Mashima's already laid down all the cards, and we're now (definitely) heading towards the endgame. Now that I think of it, the double chapters we're getting is genius move on Mashima's part, (or the publisher's part).....
It's part of story telling that has conection to the end of manga. And why would it get resolved long time ago if It's part of the mystery, and the revelation will happen in the end or near the end of the manga.
Not all jump mangaka do that. Inoe takahiko doesn't do that, why doesn't show the final and the manga end in the semi?
Onepiece world is big, Ofc he will not touch all of it. One thing for sure, there will be big war that tie with one of onepiece theme, oppressor vs liberator.
I know you're mashima fan, but he's not a genius. He's more a hardworker. The most hardworker perhaps.
Kishi goes to newyork? Well, expecting another justification and retcon.