Then, IMO it is best to substitute pot with discrete resistor(s). Add a grid stopper resistor, and maybe an additional gread leak. B+ will be about 200V, and Uak~100V-110V. Two cheap red LED in series, and bias voltage Ugk will be about 3,4 - 4V. Ia=15mA seems fine. But, anode of the LED (longer lead) must go to the tube cathode, and cathode of the LED(shorter lead) to the ground. When we reach the final design, I can PC-draw it and send.