So, good news is that your sde is detected by all tools normally.
If you boot an USB stick I would expect that you could chroot into your system by opening a terminal window and enter
sudo manjaro-chroot -a
(select 1 if only one system is offered)
Then run
pacman -Sc
This cleans your package cache.
Afterwards
pacman-mirrors -f && pacman -Syyu
exit
and try to reboot normally.
All your settings are located in
/home/$USER/.config
/home/$USER/.local
/home/$USER/.kde4