[morzh]

Well, digital meter reading is pretty close to where it should be.
I suggest you use it for consistency.
This kind of confirms, you should look elsewhere.

I suggest an experiment:

Put the volume pot to the max, while tuned at a known station that will not ruin your speaker or your ears. It should be loud enough but to the point where you can tell for it to become less loud, or more loud.
Also, have your tone control switch to the "Middle" position (where it does not affect the sound). This is the one in the middle, where nothing is connected to the the contact.

Then disconnect both C61 and C62 from the pot, and connect them together.
See if the volume has increased.
This will tell us if your volume ct is involved at all in the situation.

While at it, measure your pot to conform to what the sch says it should be.