I had similar experience
Was on devil kernel, reformatted to f2fs all workng.
Tried dual boot, was in 2nd rom
The internal storage was showing no free space, checked and I was only using 3G of the 12
System was not happy
Dropped into recovery and formatted /intsd
Recovery rebooted automatically and would not do anything,
Reboot, entered recovery, rebooted, etc,etc
Dropped into download, Odin flashed cwm recovery,
Formatted partitions back to ext4, restored nandroid.
All back to normal....
Leaving f2fs alone for now