Three hot wires,1 neutral on a switch
Based on your readings, the 1 side black, 2 side white(! retag this wire with black electrical tape!) and 3 side black should be nutted together and pigtailed, and the 1 side white should be pigtailed to the 3 side white apparently -- there looks to be some sort of load plugged into the outlets connected to the 3 wires, which'd explain why the 3 side white reads 120VAC with regard to the 1 side white.  From there, you can then connect the white pigtail to the silver screw, the black pigtail to the lower brass screw, the 2 side black to the upper brass screw, and the bare pigtail to the ground screw.

The funny voltage readings on 2B with the switch off are due to the high impedance of your meter seeing capacitive coupling of a small amount of energy into the switched-off wiring.