Amhlaoibh Ua Súilleabháin has the planet Earth marked out as "An chruinne" in his 1828 diary. Similarly Planet Earth is marked as "An chruinne" in Slighe an eolais by Cormac Ó Cadhlaigh (1926). It has the meaning of "globe" as well.
For me "an saol" or "an domhan" is closer to world.
An domhan can also be used for planet Earth.
By the why, native speakers also used "An Talamh" to refer to Earth astronomically.
In "An chruinne dhomhanda", domhanda would indeed read as "terrestrial". That's a poetic/literary phrase, usually used to complete meters. It would "The terrestrial sphere/orb"
Cruinne also means a sphere/orb.
An Talamh = The ground, very rarely: Earth
An Saol = The world, but particularly the human world, as in "The world was shocked to learn that market prices had fallen globally"
An domhan = The world, usually as in the surface of the Earth, as in "Across the world, in all parts of the world". All of terrestrial geography if you will. Sometimes used for Earth, under influence from English.
Cruinne = A globe, orb or sphere. Also the most common native word for Earth. (It and Talamh are really the only two pre-1900). Also: The universe
The simple rule of thumb is that the "n" in "an" is always pronounced, except by people whose dialect sometimes skips over it. If you have to ask, you should pronounce it - leaving it out won't make your Irish sound any more natural, and by the time your Irish does sound more natural, you may find yourself skipping over it anyway.