1&2, The LP-16 compatible with USB 2.0 and USB 3.0 HDD’s and SSD’s as well.
You need to know there are the quick export mode in the uTool, this can be solution if you already have the audio content on your drive but you need to change something in the mixer or playlist in this case only the settings file and playlist (*.set; *.play) exported to the drive, which really fast.
You can also try to export the content to your local drive on your MAC than copy the content to the drive. (if you using this method, please make sure you copy the right folder structure to your drive.)
3, Good to hear finally you solved the firmware update issue. Sorry for that.
4, I’ll add this message as user feature request.
Can you please confirm your uTool version v2.0.34 ?
If you still not able to playback the songs please send me the *.set files form your songfolder on your USB drive. support_at_cymaticaudio_dot_com