thanks for your detailed debug info. I found a bug in Bluetooth, that prevented some speakers from working (Pulseaudio Bluetooth drivers Bluez5 vs Bluez4) and I built a workaround during connect and added better information to the message output on the connection status.
If you had problems connecting your speakers until now, get the latest Beta on the Settings Page of Max2Play, remove your speakers from the Bluetooth page, Scan again and click Reconnect next to your speakers.
@stefano: is your smartphone is indicated green (connected)? Can you post the output messages when clicking “Install Squeezebox Server Streaming”?