[Gromoljut]

Concerning Old Church Slavonic: no modern Slavic language is in any way the descendent of OCS, but the latter features in many as an adstratum (literary russian is particularly known to have borrowed many words, sporadically, from OCS - native голова vs borrowed главное instead of the expected головное, ...).

Consider this: Old Church Slavonic is a literary language. The difference between actually spoken language/dialect and literary language can be described most easily like this: if spoken language is a child, then a literary language is the photograph of this child. The child grows, the photograph stays the same (or you make a new one, ie update/reform the literary language). When the child is adult, it has children of its own (East South Slavic branching into Macedonian and Bulgarian dialects), and one may or may not decide to make photographs of them. If there are none, all we can do is reconstruct their appearence judging by the looks of their descendants and other relatives ("uncles and aunts" - which is what OCS is to Macedonian and Bulgarian).

As for modern Serbian đ and Macedonian ѓ, these have absolutely nothing to do with děrvь. They are the reflex of psl. *d'. The most famous word, used to illustrate this, is *med'a - sln. meja, sb./cro. međa, macedonian меѓа, bul. межда, pol. miedza, cze. meza, rus. межа, ...
Děrvь is a letter derived from Greek and was only used in loanwords like ang'el and evang'elije (but - at least initially - it was indeed spoken very similar to modern Macedonian ѓ).

If one takes into account vocabulary, Bulgarian and Macedonian are most likely closer to OCS than any other Slavic language.
Grammatically, anything can be said. No Slavic language has conserved the whole Protoslavic grammatical system. Some languages have the vocative (Croatian, Serbian, Bulgarian, Polish, Czech, Ukranian, ...), some have dual (Slovenian, Upper and Lower Sorbian), some have definite and indefinite adjectives (which emerge sporadically in different flexioned forms of the adjectives), some have aorist (Bulgarian, Macedonian? - I am not sure), some construct the future tense in the same way ("to be" in the future tense + active participle - sln. bom znal, cze. budem znal, pol. będę znał, ...)
And, last, phonologically: I am sorry to dissapoint you but no modern South Slavic language is in any way closer phonologically to OCS than modern East Slavic languages (and to a lesser degree Polish). OCS separated hard from soft consonants, hard ъ from soft ь, hard y from soft i, jat from e (and a), nasal vowels from oral ones (only Polish and Kashubian retain nasals), ... No modern South Slavic language makes such distinctions.