I remember a while ago someone asking if Audible download manager on PC was accessible, and I just went through the download manager and messed around with the different keystrokes, because when I oogled hotkeys it was rather impossible to find lol.  Hope this can help people who are considering using Audible, because the PC program is totally usable!  I use it on Windows 8, but I've seen plenty of guides for the Windows 10 app version as well. 

Note:  This is specifically for the Download Manager that you download to your PC, not any app version.

Audible keyboard shortcuts:
Play/pause:  control  P
FastForward:  control  F
Rewind:  control R
Skip forward to the next chapter:  Control shift F
Skip back to previous chapter:  control shift R 

I haven't been able to figure out any volume controls, and as far as I know you can't speed up the speed of the audio book.  Hope this helps people!