Just out of curiosity, how many words in the Church Slavonic dictionary (say, from 10 randomly picked pages) would you say are exactly the same as modern Russian?
I don’t have a Church Slavonic dictionary and could not find one online. I will do some random scheme using the scripture link you gave me, later.
If I were to guess, I’d say 80% are guessable, and 40% are the same. But as we’ve seen, most difficulty is in grammar and auxiliary words, which are not close. On occasion, you might run into changed semantics as well.