Those Magnificent Television Tubes

[neodymium]

But 390 Vdc and 6400 Ω plate to plate load, as named in the schematics, would make 35 watts of output power impossible.

35 W is absolutely correct. Raa=6400 ohm, but the real load is 1600 ohm at half primary winding to anode at class AB (at peak output). The peak current is 210 mA, peak voltage is 335 V (at half primary, of course). 55 V remain at anode