BMK2 used in cathode-biased amp

[Champ81]

Thanks Kevin

First question:
Its the terminologies that I'm confused  with. Essentially both fixed and adjustable cathode bias are doing the same thing. Varying current between the cathode and grid. In both cases the grid is always negative with respect to cathode.  At first I was thinking the term fixed bias is when a current can be varied/adjusted via a potentiometer or trim pot.  And a cathode bias is a non adjustable bias circuit where the cathode resistor self biases the tubes.  With the circuit I currently have now would it be correct to say it is now a fixed bias? Or a variable cathode bias amp.

Second question:
I am also under the understanding that in a cathode bias the grid is negative with respect to the cathode via the resistor which makes the cathode more positive with respect to the grid with rhe grid being at zero. In a fixed bias a negative voltage is applied to the grid while the cathode is grounded. But I cannot see how you could apply a negative voltage to the grid.  For example with tubes out you can measure the voltage from the grid to the chassis and there is a negative voltage. Is there a negative voltage via the grid leaks?

Edit:
I have capacitors rated at 25V across the wiper and pot "o". The voltage measured across it is around 35V and sometimes goes up more depending on the bias setting. I ordered a couple more caps rated higher. I'm surprised that these caps didn't explode. I didn't measure them when playing and realized up until now.