We're online at the same time - I was just typing up section 9. Let me start over.
Your edit worked but the audio level of the 3rd verse was enough lower that Checker shows the overall level is out of range.
In Audacity -
Select the 3rd verse of the Toothbrush Brigade poem - for some reason the chorus you added is louder so leave that out of the selection.
Use the Amplify effect to add around 6 dB to just the selected portion.
Then, to make Checker super happy, select the entire recording and use the Amplify effect again to add around 2 dB to the whole thing.
Export again and upload to LibriVox.
If you wish I could probably make a video showing how I would do this. Let me know if you want to go for it yourself or you want to see a demo.