To the ones blocked at umount-mmcblk1p1 errors:

I was able to boot NITDroid today, doing this (I don't know if it's very adequate, but worked for me)

-umount mmcblk1 if you don't have mmcblk1p1. If you can't, read third line here.
-AFTER sfdisk, REBOOT.
-WAIT until tracker and tracker-indexer stop working (conky will help, these two process are the ones consuming 99% CPU for about 6 minutes after reboot, preventing you for umounting mmc!
-Then you will be able to mkdos and mke without errors