OK I got sound back, via first fixing my Bug#802847: XDG_RUNTIME_DIR warnings problem, then installing pulseaudio and pavucontrol and alsa-utils. After fiddling as much as I could with pavucontrol I then turned to alsamixer, where as non-root I turned up the single pulseaudio control. And voila, speaker-test finally made real sounds!
And indeed the whole kaboodle even lasts through reboots! However this is still no excuse for trying to read / write to /var before it is mounted or after it is unmounted!
