Glad you are enjoying the sound! We know about the volume control bug and have a fix ready. Development for the paid version is proceeding nicely.
Regarding sleep, the audio stream does have to remain in use for DPS to function properly. However, we addressed this issue in OSX by polling for the presence of audio and shutting down the stream while not in use. I’m not totally sure this is possible in Windows without causing some glitches. I will get with our programmers on that.