Thanks for the comment, Michael. You've made me think harder about how to treat "rigor" and I've changed my translation for that (not the change you would expect, though). On the other two points I disagree with you, but it's good to be asked about them - keeps me awake and checking what I've done.

The definition of "darling" in the Oxford English Dictionary (the leading and generally considered definitive dictionary of the English Language) is " A person who is very dear to another; the object of a person's love; one dearly loved." We don't say "loved one" much, we tend to say "darling" instead - all us speakers of British English (Scots, Irish, Welsh, Northern England, Western England, and south East England) variants all have the word "darling" and it means roughly "dearly beloved" in all of them. Obviously the correct translation, isn't it?

We don't (in English) say "faithful one" unless there is context that has an antecedent for "one" to reference, it invites the question "one of what?" so we use the stock phrase "faithful admirer" instead - that's the normal English idiom when referring to someone who loves someone.

Rigour has too many possible meanings to be useful here. If I were trying to translate to 18th century English I could use "rigour", but I don't think most people would understand what the possible meanings of that word were then, and I'm trying to translate to current English anyway. But maybe "hard" isn't the best choice here (it too is ambiguous). The context calls for "strict" or "harsh" - but not for "stiff" (makes no sense) or any of the other 36 meanings listed with citations in OED for rigour/rigor for Modern English (but not for any of the meanings listed for rigor but not for rigour) and not for any meaning that first popped up later than 1800. If I'd been thinking about the date (and about what the word probably meant in Italian in the 18th century) when I wrote the translation I would not have used "hard", I would have used "harsh" (which may be wrong - perhaps it should be "strict"). The word now spellt "rigorousness" used to mean (when it was spellt "rigoesnes" in middle English) "strictness" and could still mean that in 18th century modern English, but can't mean that in current modern English (it now means either "being detailed, accurate, and thorough" or "scrupulousness" neither of which would make sense in this aria. Picking up the obvious word "rigour" just because it is a descendant of the word "rigor" that was borrowed from late Latin at about the same time as "rigor" was inherited from late Latin by Italian makes no sense when it has so many possible meanings in current English that they are almost all obviously wrong.

So your comment has woken me to a careless error, and I shall change "hard" to "harsh" and "hardness" to "harshness" (both are needed).

It's quite irritating to be able to use "harsh" in the translation (because although rigor is a noun English needs an adjective) but needing "harshness" in the footnote.