Answering my own question here:
It turned out to be a fairly trivial solution - here's to not checking over your setup carefully enough.
It all came down to adding 0x2080 (the nook touch vendor id - which happens to be the same as the nook color vendor id - you can verify by using lsusb on linux) to the ~/.android/adb_usb.ini file, which basically just tells adb to look at additional vendor ids. This is stated clearly in the nook color docs, and I could have sworn that I did that hours ago, but when I re-looked at the file, I found mine was blank
. As soon as I added 0x2080 back, everything started working perfectly.
Note, this is necessary for both mac and linux.
And, it doesn't matter if your NST is on the "Usb mode" screen or not; I got it to work both ways.