Should questions with vague or ambiguous titles be edited to more specifically indicate their contents? If so, with how heavy a hand (i.e. how much deferrence should be paid to the poster's right to expression at the expense of intelligibility)?
In my opinion, yes. To make it easy for people to see, from the front page, which questions they may be interested in reading the details of, the title of each question should do a good job of conveying what the question is about.
People with editing power should enforce this, using as much of the original title as possible while still making for a useful title. I think that the author's expression should be a distant second in priority here, since the main point of a title is as I've described above. The question body provides more room for free expression.
I don't know if we ought to go back and fix up what may be hundreds of existing unclear question titles, but if you come to them, particularly if they sit atop particularly useful content, I'd encourage you to go ahead and make them clear.
I've edited the titles of the second and third examples you linked.