The "rm failed for MoxierMail, Read-only file system" error is because you didn't use "adb remount" which is what allows you to make changes.
Try typing "adb remount" before entering adb shell. That worked for me the 2nd time I had to root. I'm not sure if it's because I updated the FW to 10f.
I think the "mkdir /sdcard/backup" error is because you're not in adb shell and/or you didn't enable "adb remount".