That filter is mounted on the inside of the firewall. The picture is of my 40, the orange / brownish looking hose attached to the firewall is what your looking for. The small metal pipe sticking out of your firewall.
My 40 has the large style drain plug and would seep. I started using this plug seal / washer with a bonded rubber inner lip, from a company here in Denver. Their website is Rocket seal.com I can’t come up with the part# right now but I know the inner diameter is 1 inch. No sealer, wipe it off...
Just take the other end of the wire you have clipped to the solenoid body off the meter and touch ground! Then it should click (or not). You are overthinking this.
I don’t have a diagram for you, but if you’re referring to A/C wiring on the engine side of the firewall the additional wires probably go to a low pressure switch attached to a low pressure hose.