I want to be able to use ELU.SE to help promote proper usage of the English language (in specific: synonyms, definitions, and spelling). How can this link (below) be added into the FAQ section to let users know how to improve their English language skills?
for your title question there are:
For your first sentence, ELU is populated more by descriptivists than by people who want to enforce prescriptivist standards. Which I would say is actually better. The people you inform will get more than just a standard answer but also the variants by region and formality. But more often than not, you'll get a single answer for just one variety or one level of formality and not necessarily the 'standard' one. Also, there is more than one standard, and even within a standard there is disagreement. So you might get that nuance or not. What I'm saying there's no guarantee here of getting the 'right' answer.
For that link in particular, I'd say it would go best in the 'General Reference' question I just mentioned. And you can go edit it yourself. Since you don't have a lot of rep yet, it won't automatically get edited, but a high rep person can approve the edit.
- but in general, to add something to the FAQ, start a question here (specifically about the edit) and a moderator might be convinced to edit it (normal users can't).