I added about 300 words in details and hints to earlier chapters. Somehow, the "mere sentences" left in chapter 15 expanded to fill the rest of the day's word count. I stumbled across some first draft infodumpy bits that I had cut from an earlier scene, and realized that they belong in this one.
So I'm still on chapter 15. But this time it really is mere sentences left! (I think.)
One-third of the way through the month, and on track to finish Act 3 (of 4) by Halloween!