Hey, it does work with OSMC / Kodi, and Pavucontrol was necessary to get it working, see Pisound + Kodi?
Pisound appears to the OS as an ALSA capture and playback device (usually hw:1,0, specifying hw:pisound should work too), so it should be usable with all modern Linux audio applications.
I haven’t used OSCM / Kodi much, so I can’t comment on 2 and 3. 