There should only be one /dev/uinput
It looks like uinput is working- I’m not sure what’s causing picadehatd not to be running in the background at startup, since everything seems to be installed properly.
The uinput errors in the log file could have been a red-herring from running it as a user, rather than as root.
sudo picadehatd and seeing if that gets you up and running.
Absolutely, yes. The soft power off functionality requires picadehatd to monitor the pin state and issue a shutdown when it’s held for 3 seconds.