A likely effect of performing gratuitous edits (or ones perceived as gratuitous) is that you irritate a lot of people, some of whom will flag for moderator attention. A small handful of small edits may fly under the radar, or otherwise might be excused, but I'd say you have to be careful/thoughtful. (I think this is consistent with the answer given here, mentioned by Martin, to a slightly different question.) Indeed, some users have been known to exhaust the patience of the community with dozens of tiny edits.
I'd like to add a general rule of thumb: whenever you edit, you should make a good faith effort to catch as many blemishes as you can at that pass. Put slightly differently: holding a few blemishes in reserve for a future edit is, one could argue, a form of dishonesty.
I think that addresses your first question.
As for the proposal (set off in a gray box): I agree with Asaf in the comments that it's not a good idea, for reasons he mentions. From there the comment thread is largely about how to interpret a lack of response to a question that has been upvoted.
I see three likely explanations:
The question is so hard that even experts are stuck.
The question is not that hard, but people who could answer haven't seen it yet.
People who could answer (if they wanted) have seen it, but for one reason or another they have not been moved to reply.
If it's the first scenario, patience is required. Hopefully the question is both so interesting and so challenging that it will be upvoted a lot, so that someone will be motivated to answer and claim the prize.
In addition to crafting an interesting well-written question, precise and thoughtful tagging may lessen the chances of the second scenario. You can get a better idea of whether it's gotten good attention by looking at page view numbers, more so than by counting votes in my opinion.
I would guess that oftentimes, we're actually in the third scenario, which is unfortunate. I regret to say that my own reaction to a lot of questions where I have some knowledge is a firm "meh" -- it could be that I think the question is lazy or poorly researched, or arguably/suspectedly below the level of the site, or too tedious, or maybe even too rebarbative (e.g., the OP seems likely to want to argue with me) -- whatever the reason, I may feel that the question is, for me, not worth the bother of putting together an answer. If others feel the same way, than generally speaking, small edits are not going to cut it in this case, and could very easily backfire.
Just as in writing papers, in many cases you can't make people get interested unless you explain why it's interesting, or why an answer is so important. I apologize if this advice sounds like boilerplate, but in my opinion the advice is not heeded nearly as much as it should be. Giving background can help a lot. Giving evidence of trying hard to find the answer yourself can help a lot. If knowledgeable people see that you've been knocking your head against a wall for an hour or more without success, and tried hard to ask a question with care (even down to small details), then the chances are much better you'll be lent a sympathetic hand.