I heard about a new reorder script that sounds like it does almost exactly what you want. I’ll try to find the name of it in a moment.
I believe this script does what you want
As for this…
I’ve done that a lot of times by doing just a bit more than the forecasted incoming reviews. You do have to adjust for missed reviews, but it does help them whittle down gradual. Like say you have 50 reviews coming tomorrow. Do 55-60 reviews. Double check the incoming number (maybe now it says 70) and then do the difference plus 5-10 more reviews. It definitely takes time though.
Can I also ask what your goal is with studying Japanese? In most cases grammar is more helpful than kanji. Also it sounds like you might be doing what I used to do- use WK as a crutch. Because it feels like you’re making progress by studying kanji because srs is simple and easy to do. However though, when it comes to learning Japanese, there are better and more worthwhile ways to practice, even if they don’t have that same easy effect of seeing reviews go down. Things like reading or practicing speaking, all depending on your goal. 3-4 hours of kanji nightly isn’t going to take you as far as trying to do something like read something at an appropriate level or talking with a native speaker. Just dropping that since I had the same problem and now that I’m focusing on grammar, production, and reading, I’m seeing my Japanese improve a lot more than before. Been there, done that. I hope you avoid burnout and get some good sleep.