Hey, looks like you may check out the log of BabelPod by running:
journalctl -u babelpod.service
It could be that this software expects 44100 sampling rate, while Pisound natively supports 48000, 96000 and 192000. To make 44100 work, software resampling has to be set up, by creating an asound.conf file as described here:
Try doing everything but commands directly related to Raspotify.
Then if possible try to use ‘default’ audio device. If that’s not possible in BabelPod (I don’t see ‘default’ selection in its screenshots), you may have to do it via loopback device as described on Piping System Audio to Airplay (updated September 3rd, 2018).
Probably if you contact BabelPod developers, they might have some insight as well on how to get it working. 