You have to say what the switches are set to... measurements show the function switch was somewhere like Bridge, so they are not so helpful to troubleshoot leakage function.
Working backwards, the 6E5 magic eye ray-control triode grid voltage is -43V so it is hard cutoff 0º shadow; 0V gives 90º shadow. It should be a few volts negative, around -1V.
6BN8 cathode pin 9 should be +0.45VDC and you are getting -2.4V? That does not make sense unless it is oscillating. Anyhow, the bridge was way off balance when you measured voltages and the tubes are OK.
I would set to a low voltage and measure in leakage test. V2A and the trimpots and both sides of the 1.5MEG R6. Your multimeter will load down the grid side.
I recall you can damage the Heathkit IT-11:
If the cap-under-test is shorted, during a leakage test or
If you short the (+) lead on the capacitor-under-test to ground during leakage test, charging on a HV setting. It cooks some resistors on the voltage switch, it was like R30 down as they are not 10W like R40.
Check R35 47k, discharge resistor R36 680R and 1.5MEG R6.