Personally I think that act 3 ends in chapter 1006 or 1007.
My prediction Chapter 1004. Name: "Open" or "My Equal"
My prediction for 1004 is that zoro is keeping distance holding luffy. Law agrees to teleport him. Luffy is teleported to the location of Yamato. It is then revealed that yamato is being chased by Jack. Jack is already healed up and is going after yamato who now has luffy in her care as well. She wants to fight jack since she is confident in her abilities to defeat him but now that she is watching over luffy; she doubts that she can actually beat jack while also protecting an overly exhausted future pirate king luffy
We pan over to sanji being chased by black Maria. Brook and Robin intercepts black Maria giving chance for sanji to run elsewhere. Brook and Robin vs black Maria and her subordinates. We also see nami and Russo along with Tama taking out fodder.
Scene switches to Sanji sensing luffys presense being faint so he rushes over to luffys direction. Coincidentally drake is also on his way upon sensing jack chasing yamato and co. Queen looking up from above sees this and jumps down to where Jack is at. We see jack and queen standing side by side. At that same moment sanji and drake show up there together at the same time protecting tired luffy and yamato . Sanji goes heart eyed for yamato. And he tells her to watch over luffy.
Yamato promises to watch over luffy and momo. Yamato is worried having a convo with luffy about him being the heavy hitter and not apart of the fight against kaido and bigmom right now. She is afraid for the lives of the other fighters. Luffy then responds to her saying that "he has left zoro with the rest". We see a flashback before law teleports luffy to yamato with zoro promising luffy to hold the fort against kaido for 10 mins. When yamato asks luffy how can he be so confident in him. Luffy responds "because ........."
Scene goes back to the fight. We see zoro looking at kaido in hybrid form. We then get a zoom in on zoros face realizing that he now has his second eye opened. We see zoro has finally stated that he will take it seriously and proceeds to enter the state of ashura with luffys dialogue to yamato being "because he is my equal"
Pretty great fanfic, unfortunately Oda will never confirm or deny the gaps in power scaling between Luffy, Zoro and Sanji.
Oda knows what he's doing, shit like Luffy vs Zoro, Sanji vs Zoro, Mihawk vs Shanks. All of this is Oda creating debate for the community, he wants to make the community active with this kinda of stuff. Just look at chapter 997, he knew exactly what he was doing, from starting the chapter with that cover page and then everything he shows after that. He manipulates the fanbase and their discussions, masterfully, and he knows the community and the mysteries is what keeps One Piece going. So yeah, Oda will never really confirm the gaps between the three. It will always be Luffy >= Zoro >= Sanji, and he will never say how far Zoro is from the 2 extremes.