Just wondering out loud here, but does the kindle allow you ibtype in the mmc0 password on the kidle keypad, or do you have to connect to th recovery port, I know that with my patched kernel, you can press "3" to export mmc0, even though nothing was printed on the screen. Can you type in the password even though nothing appears on screen?
Someone can test my theory by restarting into recovery menu by holding Enter. Then in there, press 3 (or Alt+E on DX). Nothing should change on screen. Then type in your recovery password "fiona#####" and press enter and see if you see mmc0.