which instance of theseu’s ship am I?

Rollercoaster Tycoon 2 or possibly OpenRCT2 (depending on whether or not it works on the hardware)

https://github.com/audiamus/AaxAudioConverter

This should be able to split them by chapter.

I bought a few books off audible, and while I can still access them even without a subscription, I still have them converted to mp3 on my NAS, in case I ever lose access to audible for some reason.