Note: Australia is generally considered to be a continental landmass, rather than an island. If however one does count Australia among the islands it, not Greenland, would be the largest in the world (unless one also considered Antarctica an island).
... (I) in the second line is nominative. na caaham =
"...and not I....", meaning "but I am not...".
"teshv-" (in/at/by them) at the end of the second line is in ...