Best approach to mature cards 3 weeks before exam

Hi guys, I've got a deck of about 4000 cards for my fellowship boards. At this point I'd say around 2500 are mature, even of the remaining 1500 that are still 'young' I wouldn't be surprised if at least 50%+ of those were mature enough for exam purposes if not for me just wanting to see if I could nail them perfectly and hence hitting again (I've probably seen all cards many many times now over the past 4 months of non-stop studying so nothing that comes up is unfamiliar).

My exam is 20 days away so at this point I'm wondering if I should shift gears to some extent and try to hone in on the young cards, anki is currently feeding me about 200 reviews a day which I don't think will chip away at as many cards as I'd like before the big day though I recognize that ultimately you can't rush the process, frankly I just need to see everything and pass the exam, it doesn't matter to me if I don't remember it a week after the exam what matters is that I know it as well as possible on the day off.

Questions:

1. Would it be worth creating a filtered deck at this point, setting it to capture all cards with < 20 day intervals and then blitzing through those? Note my cards can be a bit dense and self made and it's a hard short/long answer fellowship exam, so my review times per card average 30-40 seconds. On a good day I can get through like 600-700 cards in a full day of studying and it's exhausting.

2. Should I have anki reschedule based on my filtered deck or does that screw up the algorithm?

3. If I adopt this approach what do I do about the mature cards that come due?

4. I'd ultimately like to focus on what I'm weaker at and free up some time to read up on guidelines etc. and other practice content I need to sharpen up.