1. Do we not now know that the "grace of *** that bringeth salvation hath appeared to all men"?
– and in most 'rhetorical questions'.
If you're writing 'literary' English, it's permissible to omit the question mark after a rhetorical question; especially in a passage of fiction that is supposed to represent 'thought'.
Yes, you need to use a question mark at the end of all questions, rhetorical or not. Here, because the original quote is not a question, but your sentence is, albeit a rhetorical question, the question mark goes outside the quote, and you lose the end stop period. It should look like this:
Do we not now know that the "grace of *** that bringeth salvation hath appeared to all men"?