The latin and greek wordstock in modern languages come from ancient latin and greek
1: they come from both (trottoir, abattoir, cache-nez, plage, use, attack, develop), likely more from the modern tongues (use 1: you shouldn't be saying such mean words anyway and 2: if you do come across them knowing French or Spanish will be enough to know what they mean almost always. And even if you were right, there is Latina sina inflexione (Latin without inflections), a tongue designed to teach mainly wordstock in the sense you mean and to understand any Latin writ. There's also Slovo for Slavic tongues - better than learning Old Church Slavic that has much changed or something like you would suggest. There are actually several tongues like these designed to be understood by each member of the mix of tongues, and also to teach wordstock.
That's definitely a plus!
K, spend literally thousands of hours to just read...what again? I'm pretty sure no book in the top 100 most-selling books of all time was originally written in Latin. Look at this whole list, nowhere is Latin written here.
https://en.wikipedia.org/wiki/List_of_best-selling_booksEsperanto isn't very useful either but at least it is part of a noble goal.
Learning "1% of a language" is like learning none.
Esperanto roughly takes 2/3 of its wordstock from Latin roots and the other 1/3 from Germanic with a few Slavic words. Zamenhof never knew any tongue besides Indo-European ones.