2896 towb טוב pleasant, agreeable, good
While 2896 could refer to "fit for purpose" (in the sense of "agreeable"), it seems to be a stretch. More likely, it simply means that Elohim was satisfied with his accomplishments. There isn't anyone else around to say "good job", so he says it himself. Notably, 2896 is the same word used in Genesis 3:6 to describe the fruit of the Tree of Knowledge of Good and Evil as "good for food" – agreeable for eating – not poisonous.
3966 meod מאד muchness, force, abundance
Genesis 1 is poetry with a lot of repetition and alliteration. The "very" comes near the end. Each of the preceding elements was "good", so in aggregate, they're "very good" – or abundantly/exceedingly good – the sum is greater than its parts?
It's not prudent to place too much theological emphasis on specific readings of particular words and phrases. Otherwise, it would mean that Elohim literally pounded out a solid, physical barrier between earth and heavens to keep the waters above and below separate (Gen 1:7). Although modern translations tend to hide this view, there have been, and still are, major disagreements between astronomy and religious cosmologies.
7549. raqia: an extended surface, expanse
7554. raqa: to beat, stamp, beat out, spread out
A primitive root; to pound the earth (as a sign of passion); by analogy to expand (by hammering); by implication, to overlay (with thin sheets of metal) -- beat, make broad, spread abroad (forth, over, out, into plates), stamp, stretch.