If you stand at the front of the engine, the alternator is on the left. Just to the right of the alternator there is a little dashpot that has an easily accessible vacuum line attached. Start her up, and pull that vacuum line, and put your finger on the hose to see what 17 - 18 inches of vacuum feels like. Put it back on, and turn off the engine.
Now back inside the car. As we know... the black hose is the vacuum source.
I guess I would pull the front switch that controls the front vent actuators. I'd want to know if I have vacuum that far. So close off the black hose that goes to the rear controllers with a piece of tape. Then test the black hose for vacuum to the front switch. If you have no vacuum there... then you will have to trace it back to its source, as you have already been trying to do. IF you HAVE vacuum there... then you will have to come up with a way to test the integrity of each of the different colored vacuum lines, and the actuators they are attached to.
One way may be to see if you can find a plastic insulated wire that will fit tightly inside the connector, strip the wire out of it, and use the insulation like a straw, and then test each of the colored tubing by drawing vacuum with the straw. If it holds vacuum, then that one is good. If they are all good... then the switch is bad.
I don't know what that green stuff is.
If some one has a windstar EVTM electric and vacuum troubleshooting manual, they would be able to tell us which colored vacuum line goes to which actuator.
For others who are not completely following this post in one of the pictures above, you can see the middle switch has red, blue, green, yellow, and orange vacuum lines (they look like wires) each if them affect an actuator that directs the air to to the various vents in the front. | 
