Yes 3 is connected to the primary. But that is not where the problem would lie, and I doubt that your parafeed capacitor is "blown" if it has 400v on one lead and 0 on the other. Caps short when they fail.
If you look at the schematic you can see that the low end of the OT primary winding connects to the cathode of the output half of the 6FJ7. The cathode should be around 18V and that would float the end of the parafeed cap up close to that voltage. So check pin 7 of the 6FJ7 on that channel and see if you have around 18V.
My knowledge is lacking o really understand what i going on here. but if I am to understand what you say, I must test pin 7 the voltage at the white circular socket that holds the tube, under the chassis, and on the side with no audio?
If that is the case, when I test pin 7, I get a very low reading in the tens of millivolts range, but oddly it starts to ramp up and keeps going to around 200mV within about 15 seconds, and I guess it would keep doing so. But that must be the meter doing funny stuff?
What does it mean? What is up with the slowly climbing or descending readings, and why are some readings preceded by a minus (-) symbol?