Breakdown of Fríhöfnin er um það bil að loka.
vera
to be
það
it / there (existential) / the one (n)
að
to (infinitive marker)
um
about
Questions & Answers about Fríhöfnin er um það bil að loka.
How does the phrase um það bil literally translate, and how does it create the immediate future here?
Literally, um það bil means "around that interval" or "around that space." When paired with the verb vera (to be) and the infinitive marker að, it functions exactly like the English "to be about to [do something]," expressing that an action will happen very shortly.
What are the components of the compound word Fríhöfnin?
It is made up of frí (free) and höfn (harbor or port). The -in at the end is the feminine singular definite article. While it literally translates to "the free port," it is the standard Icelandic word for a duty-free shop.
I recall that the verb loka usually requires a dative object. Why is there no dative word here?
You are right that when you close something, like a door, that object must be in the dative case. However, in this sentence, loka is used intransitively. It simply means the shop itself is closing, rather than the shop acting on a direct object to close it.
Could I use ætlar að loka instead of er um það bil að loka to talk about the future here?
You could, but the meaning shifts slightly. Fríhöfnin ætlar að loka translates more closely to "The duty-free shop is going to close" as a general planned event. Using er um það bil að specifically emphasizes the immediacy of the action, meaning it is closing right this very minute.