HP conference screen to MB12 via satechi hub

I've just bought a HP elitedisplay e240c conference screen with built in speakers, webcam and microphone. I'm using a 12" macbook retina running Sierra 10.12.5. The USB-c is connected to a powered Satechi hub which connects to the hp screen with HDMI.

The video output to screen works perfectly. I can also get the macbook to output sound to the screen's speakers. However, I can't select the screen as an audio-in device, nor does the webcam fire up when software activates the camera (such as photo booth).

I've been in contact with HP support. They don't have any OS X drivers and basically can't help me. They say the screen is supposed to work with Windows 10, and can't guarantee that everything will work with anything else.

QUESTION 1: How can I get my MB12 to detect the hp screen as a webcam and a mic?

QUESTION 2: I'm currently using the Satechi with NoSleep (software) to make a pseudo-dock for my macbook. It doesn't work very well with audio ouput. When I close the lid, the hp screen goes momentarily dark and then comes back, but the audio output returns to the (now closed, hence muffled) macbook and stays there. I *could* just keep the lid ajar, but I was wondering if there was a more elegant solution? Preferably a REAL dock that turns the macbook into a stationary computer with all external outputs fully functional while the lid is closed.