Great post, and in particular great suggestion to use it to find posts for maximizing curation rewards. Being the first, or one of the first couple, of votes on a decent post that has 0 payout when you vote it is absolutely one of the best ways to maximize your curation return (figuring out how to front run the huge votes like utopian, dtube, curie, et al is of course the other tried and true method but is less accessible to most people who don't have ability to script something to do it automatically).
RE the "slow" aspect, that is less of a bug and more the result of filter parameters that yield HUGE result sets. E.g. the one you specifically comment on for posts 6-7 days old, payout less than $2, 400+ words... has over 40,000 results currently (see screencap below)! That isn't going to return lightning fast, no. In general, better to set filters that narrow the result set down a lot farther than that, but if you want to do such general filters you are of course going to see it take a while to return results.
I've updated my post, just so I don't spread any misinformation. I'd also like to apologize in advance for any grammatical errors made in this post, English isn't my native language. Just hope I've done this project justice by writing this post.
Also, 'pending payout' are SBD values, right? That was another thing I wasn't 100% sure about.
Edit: Are you sure that 'total results' is correct? I don't think it gets updated before it has completed the query and I get 40k results standard when I open the home page.
Ah you may be correct RE the total results. Will have to check that out.