See my post at 58. It's not an anagram and it's not English.
As the preamble states, the 3-letter words are derived from the 3 16-letter entries, 3 being significant.
I think my post @71 is as far as it's possible to go without giving you the answer. It's much more straightforward than you might think. My post @65 regarding the title might help give you an idea of how to derive the words, but they're simpler than the title.
Mack, I have found a consistent way of deriving the four un-clued entries from the 16-letter across entries and these, together with the fifth word, are all similar features. However, I do not see their significance.
0pt0, you don't need to look for collective significance, just the common (consistent) derivation. It's the fifth word that 'semantically' fits the theme.