Nice idea for a quiz. How is Fiji not ahead of Samoa and Vanuatu? Also I'm struggling with where you've put Mauritius. I presume that you are including the disputed "British Indian Ocean territory" as part of Mauritius, which is fair enough. Despite being British, I agree that it should be. But if that's so, then surely it becomes further north than various other countries such as Malawi, Tuvalu and possibly Zambia?
The point I used for Mauritius is the Agalega Islands, as in the Wikipedia page. And actually Malawi just barely escapes the list but Tuvalu and Zambia are a little further north. As for Fiji, the referenced point is Rotuma Island, further north than Hiw (Vanuatu) and Fagamalo (Samoa).