I just will comment on the port issues
It is not like a land trip where if you cannot make the city on the itinerary you can stop at another one
With ships & other ports they cannot just rock up & dock they have to get permission based on availability to be able to dock
We have missed ports & sometimes the ship is able to get into another port & sometimes not
Cruising is no guarantee of making to to the ports they list this has always been the case & more so now a days with so many ships out there than say 10 yrs ago
weather is a big factor as well as unrest in some Countries
I am now the type that "go with the flow" I do not plan mush in ports I have list of things to do IF we do make the port
This is just me
YMMV