I understand בְּתוֹךְ as "in the midst of". The tree of life is b'tokh ha-gan (in the midst of the garden), and God spoke to the people mitokh ha-eish (from the midst of the fire -- the initial mem is "from"). JPS also sometimes translates a different word, ,בְּקֶרֶב as "in the midst", as it does in Habbakuk 3:2 (בְּקֶרֶב שָׁנִים, in the midst of years).
I understand קֶרֶב as "nearness". It's the same root as korban, the animal offering that brings us closer to God. Both "midst" and "nearness" indicate proximity, but in English there is a nuanced difference between the two. Does that nuanced difference exist in biblical Hebrew too, or is "midst" one possible meaning of קֶרֶב (if perhaps not the primary one)? Is there any significance to the text using one of these words over the other?
(This isn't a question about these texts in particular but about these two words. We also see the difference in Gen 23:10 vs. Deut 17:15.)