Yes, hm-us, "wenn Sie mich fragen" first of all means "if you (are) ask(ing) me" (with the meanings you mention), and my point is that FWIW is neither. To be more precise, "nicht ganz korrekt" should have said "misleading". Sophil argues the expression tries to downplay something. I disagree.
Consider: "You did exactly what i asked you not to do. I have lost faith in you, and most likely you will disappoint me again. For what it's worth, please do me this next favour."
In this sentence, the translation "if you (are) ask (asking) me" is not possible in my opinion.
"Whether or not this is of value" is close to the kind of "wenn es denn noch eine Rolle spielt.", which might be "if you still care whether..."
"wozu auch immer dies gut ist" sounds very artificial, though grammatical, it is unlikely to appear in colloquial speech.
An acronym might possibly carry some different meaning, so i would not rely on FWIW-quotes but "for what it (is) worth". Secondly, literally there is something that has or fails to have "worth".
Finally, consider this posting by R.Berg, Uni of www.Gallaudet.edu:
"i always thought of it like, "how many times do i have to tell you?" or "can't you look it up yourself?" or "you're not worth my time, here it is nevertheless..."
If this doesn't support my suggestion, it definitely rules out "wenn Sie mich fragen" (which infers being a comment to a statement like "what shall we do") and these sentences, that suggest being a comment, or side remark, emphasizing a discontent, before the comment is given.
I wish you didn't break that. For what it's worth, please be careful next time.
I wish you didn't break that. Please be careful next time.
The fwiw-comment gives the utterance a very different meaning that "if you ask me" cannot contain. So again, i do not suggest this is an alternative to the present translation, but the one given is misleading (false).
Pointing out that fwiw is more polite than iyam is ok, sort of upper and lower level of conversation/social order. Unfortunatly, none of the quoted dictionaries gave examples. Maybe "if anybody cares"? would give it some literal sense: "Wenn es denn was wert ist [dass ich das sage],...."