Looks like two chapters to go! By the way there's a echo in 5 & 6 and 6 levels are off: https://gofile.io/?c=mBnJ8a
Definitely great that you will finish this, for the reasons you stated.
This looked to help, I made a selection of 30min 02.885sec - 1h 46min 29.760sec then Effect -Amplify (Audacity suggested 7.842db amplification and -0.0 new peak amplitude). https://gofile.io/?c=IkWjvb & the MP3 https://gofile.io/?c=zyMgT7