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). I learned today that JPS also sometimes translates בְּקֶרֶב as "in the midst", as it does in Habbakuk 3:2 (בְּקֶרֶב שָׁנִים, in the midst of years).
What's the difference between בְּתוֹךְ in the first two passages and בְּקֶרֶב in Habbakuk? What does it mean that Habbakuk uses the latter and not the former?
Additional reason for my confusion: I understand b'kerev as "in nearness", the same way a korban draws us near to God. But JPS (who knows way more about biblical Hebrew than I do :-) ) translates it as "in the midst", which makes me wonder if tavekh and kerev are the same kind of "midst". Both "midst" and "nearness" indicate proximity, but in English there is a nuanced difference; is that what's happening here, or have I just run into a synonym and it doesn't mean anything special?