After pairing and connecting with bluetooth headset, check the bluetooth headset device name using 'pactl list sinks' command and then run following command.
pactl set-default-sink <device name>
As per the details provided in your query, device name is bluez_card.00_18_91_6D_B7_01
pactl set-default-sink bluez_card.00_18_91_6D_B7_01
I have tried this but the same errors occur. The problem is that the available applications that play music on the edison (aplay, mpg123, mplayer) all use ALSA to play audio but ALSA does not see either the bluetooth headset nor pulseaudio as valid devices.
The alternative would be to try to use paplay which is the pulseaudio version of aplay but I have no idea how to get that on the edison because its not on the repo. I've tried to install the rest of pulseaudio utilities from tar.gz but I get many dependency errors.
I was successfully able to play .wav file using mplayer on Dell Bluetooth headset BH200.
I run the following commands on Edison.
rfkill unblock bluetooth
pair <Device Address>
connect <Device Address>
exit the bluetooth utility
pactl list sinks
pactl set-default-sink <Device name coming in the sinks>
e.g. pactl set-default-sink bluez_sink.00_ 18_6B_4e_A4_B8
mplayer <audio file>