So, the land it's at the east side of solzreed peninsula, close to the port and npcs. All land close each other, at coast.

It's worth around 1600G each 16x16 in that region.

1000G = $33 at Gold Sellers

$1 = 32,5 FG

So we can assume 1FG for 1G

I'm doing it right?

You should be able to get 2fg for 1 igg at current rates. Unfortunately there aren't many people from archeage using d2jsp right now so it's hard to find a buyer, especially with all the different servers. Land has seemed to go down a bit in price as well. Good luck and welcome to the site.