The city light go in the small socket directly below the main H4 socket. Look closely at the unit with the access panel removed, you'll see the socket under the main. Can't remember right now if you have to twist and pull or pinch to release the city light socket.
The vacuum port is just what you suspect, vacuum adjustment of the beam. To activate you would have to replace the light switch with the Euro version plus route vacuum lines from the engine to the switch and headlight assembly. Nice feature, but one I did not activate since I have the self leveling suspension.
My DEPO's were made in Germany.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.