Let me give "answers" to these. Please note that obviously none of these are confirmed and what I say can be full of sh*t.
15- It could be nothing at all but if someone insist that something is up with the eye, did Zoro give it up for the cursed Sandai? Recently, we've seen Zoro coat CoA on the Sandai and it had a demonic aura around it. It is typical for cursed swords to want blood and Zoro has been inactive for years so Zoro probably gave up his eye(cut it himself with the Sandai) to regain control of it.
14- Bonney can only revert people from very young or very old. Nothing in between and she can do the same for objects. Any island, document etc. that the WG tried to destroy can be reverted back to its original form(younger state) like the Island of Ohara for example. Her ability alos played a big role in the 100 year war making the soldiers of the 20 kingdoms young giving them an "immortal" army to combat the "immortal" army of the Ancient Kingdom.
13- I don't think its that big of a deal. It could simply be a term for the most dangerous n' powerful pirates in the world closest to One Piece.
12- Also not that big of a deal probably. Could just be a gate built after the Void Century.
11-Creatures of the Florian Triangle- The OP world is vast and mysterious. They could be a race that we've never seen yet like titans or something.
10- Kuma was on a mission to infiltrate Marijoies and gain info on the Gorosei but he needed to gain their trust first. The only to do that was to become their loyal weapon and Vegapunk is a revolutionary spy so Kuma was fine with it.
9- The Orojackson is probably is Raftel. Raftel is probably a raft island and the OJ is probably what makes up that Raft. For a secondary place, I say Elbaf and Franky will model the Sunny after OJ a little bit.
8- Vegapunk is a revolutionary spy and is from a family of important moon people who excelled in technology.
7- The Ancient Kingdom were all Ds/ mostly Ds. They wanted freedom for the world but the 20 kingdoms stopped them. D could stand for destiny, defiance etc. and the Will of D is to bring freedom and equality to the entire world.
6- Tenquila Wolf is a bridge that connects North Blue and East Blue. It is always snowing in North Blue and I think Robin was teleported to a section of the bridge located in East Blue. North Blue is the land of the rich and a place visited a lot by the CDs so slave labor is guaranteed. The bridge has to be HUGE and made up of very strong material to withstand bad weather, explosions and some DF powers so construction would take a while.
5- Roger had No DF. Uses a gun, a sword and OP CoC.
4- Goa Kingdom was prosperous/important enough to get a visit from a tenryubitto. Goa Kingdom sucks up to the CDs and are virtually no different. Goa Kingdom was one of the 20 kingdoms that destroyed the Ancient Kingdom.
3- Uranus is the power to create and makes it wielder pretty much an immortal god. It gave rise to the clouds in Skypia and most importantly DFs. Poseidon is the power to control and Pluton is the power to destroy(destroy the Red Line).
2- Requires a loooong post on its own.
1- Half of the godly Uranus.