(Disclosure: pronunciation is my one and only favorite tag)
I may have misunderstood your point 2, but my answer is a definite NO:
I don't think all questions about pronunciation should be made off-topic.
Here are some useful divisions I see for questions (the titles are simplifications and not all questions use this exact wording):
"Correct me" questions
As Andrew Leach said, one important point against proof-reading questions is that they are very specifically tailored to the questioner, so the answer is not as helpful to other people.
The equivalent in pronunciation seems to me to be questions of the format "Listen to a recording of what I'm saying and give me feedback about my pronunciation." We have received some questions like that, but I don't think they are good questions for this site. (I don't know exactly what close reason they would fall under, but that's immaterial.)
"Who," "What," and "Where" questions
There are other types of pronunciation question. One type, "how is X pronounced?" is basically equivalent to questions like "What does X mean?" and "How can I use X?" This kind of question seems clearly on-topic to me, at least in terms of subject matter. Questions like this are often
"off-topic" in practice, but only if they show lack of research (most commonly, if the asker didn't consult a dictionary). Often additional useful questions can be asked, such as "where do people use this pronunciation?" or "Who uses this pronunciation?" Again, these questions parallel questions about vocabulary or grammatical structures.
Some high-voted pronunciation questions that I find interesting in this category:
The example question about "women" is a third type of question: a "why" question. In my opinion, these kinds of questions are frequently problematic no matter what the subject matter (and they can be asked about grammar or word usage just as well as pronunciation). They can always be answered "just because," or "it is what it is," but as medica notes, that's not a valuable answer.
In some cases, we can describe the historical steps that led to the current situation; this is sometimes what the original poster wants to know (making it more of a "how" question). I really like learning about the historical development of pronunciation. I understand that this topic is not interesting to everybody, but I think it is legitimate information about the English language, and therefore on-topic.
In other cases, we can describe the current situation by reference to other analogous examples from the modern language. This also seems on-topic to me: there is useful information about the English language in in these answers. Sometimes they are a bit subjective, but it can be the "good kind" of subjective rather than the bad kind.
Some high-voted pronunciation questions that I find interesting in the "why" category:
If it's completely unclear which of these the questioner wants, or if the original post shows no evidence of research or motivation for the question, I think it can be appropriate to close "why" questions. In my opinion, at least one thing that can be said for "why" questions about pronunciation is that it's often quite a bit harder to find the answer than for "what" questions (since most dictionaries list what the pronunciation of a word is).