One problem with trying to catch up with such a high Apprentice count is that all the items that drop to Apprentice 3 and lower would need be reviewed again by the next day, which might not happen due to WaniKani randomizing reviews. This means that your pile of reviews will result in at least double or triple the amount of actual reviews.
When I was in a similar situation, albeit with a lot less items in the queue, I installed [Userscript] Reorder Buttons to make sure that even if I didn’t review all available items at once, I would at least review those that needed it the most.
After all, for a Guru II or Master item it doesn’t really matter if it is delayed by a few days, but an item in Apprentice II will almost certainly fail if it isn’t reviewed in the expected time frame.