> enlighten with regard to the theory
Life is too short.
Triode Power Amplifer: find the plate resistance. This varies with plate voltage and grid bias, and on a "tuner" tube will vary a LOT. You want the zero grid voltage line from zero to your nominal plate voltage.
ECC86 data: http://www.mif.pg.gda.pl/homepages/frank/sheets/030/e/ECC86.pdf
Page 9: Vg=0V hits Va (plate voltage) of 20V at 8mA current.
20V/8mA= 2.5K ohms.
You have two sections in parallel, 1.2K.
For good power and distortion, the load should be double that.
For less power and lower distortion, or for high supply voltage, go 3X to 5X.
To force maximum power from insufficient supply voltage, rough-match the plate resistance. With a "good audio triode" the distortion will be a bit obvious. With this tuner triode the distortion will be gross, but not sour (up to a point).
Since your voltage is awful low, you would compare 2X (2.5K) and 1X (1.2K) loading, to see how the power and distortion work out.
In each case you "must" re-optimize standing bias to center the tube on the available current/voltage limits for that load. Put DC voltmeter on cathode bias resistor. Note reading at idle and at FULL WAIL. If it idles 0.7V and wails 2V or 0.3V, that's way too much bias shift (unless it sounds kewl). Change bias resistor until the idle/wail shift is under 50%, under 20% for "clean". Or until you decide you like it not-centered (a valid musical choice).