Showing the score of the top answer on the main page (alongside "N answers") is an interesting idea. Meanwhile, can anything be done to improve the questions?

The question quality seems to be getting better, fortunately; auto-moving all the unanswered questions with negative net votes to a separate section would be (imho) useful for attracting newcomers, increasing answer-discoverability, and increasing significantly the average quality of the main-page questions; but are you asking about improving the questions already present e.g. by rewriting them?

I was asking about improving the (currently) poor questions that nonetheless have good answers, yes. Sometimes that's a big task and not worth it, but are there any easier wins to be had? (I am not a mathematician and don't understand most of the posts on this community, so I'm not in a position to evaluate that.)

I haven't thought about it sufficiently; but there are some questions whose main issue is just prolixity and could be improved by shortening them ~90% (I haven't checked if any of them have particularly good answers). Others, like the most recent, contain only a couple points of (extreme) confusion that could be easily edited out keeping the main question intact. Still others, like the question on PA, contain multiple possible questions; narrowing them down to focus on one particular issue would I think be feasible, though. I haven't seen any questions with well-received answers (like the last two I linked to) that couldn't be shortened in this way to make good questions.