There is the ALSA layer to audio and on top of that the Android layer.
If you run the alsa_amixer it will tell you a bunch of things.
The settings in asound.conf get applied when the corresponding alias is opened.
On my USB adapter there is the playback path, the record path and the record monitor path.
Each of them has a switch to turn on and a volume.
You can play with these values in alsa_amixer.
Right now, I only have Noogie and a Windows machine.
I can't mount the other partitions or access the files.
If I were to get in the habit of bricking my Nook I'd look for a better solution.
On my Nook right now you still just have the selections of 8K or 16K,
however, it records in stereo (from a mono source) at 44100 using either setting.
Such behavior cause data overruns in Skype.
@zholy, I have no idea why your USB buttons are not working, look at dmesg and logcat.