In class AB2, in which the 6V6 which can be driven to max 14watts the 6V6 should not have more than 285volts applied to plate or screen and an 8000 ohm load is recommended.
In other words, I guess, the maximum continuous power the 6V6 can handle is 4.5Watts input, to some degree also depending on the environment but 4.5W is 'it' .
I think you don't understand AB2 class.
The 6V6 operate extremely well in AB2, as it's a transmitting valve.
(As was the 6L6 originally).
If you really want to run them in AB2 you HALVE the A-A load, but the AB2 characteristics are hard to find in literature for this valve (I have them).
They are to be found in the GE book, where they show clearly driving the g1 a good 15V positive with a cathode current of 200m/a, and a g1 current of 6 m/a
(YEP it works!).
For good reasons it's not reckoned to be a good plan to run the screen higher than 250V like this.
You can also use them successfully as a AB2 driven triode, driving the g1 up to +20V..
I was suprised to see how some old 1950s AB2 amps are run.
A pair of 807s in AB2 have a A-A load of 3k3, and they work perfectly like this, making a LOT of power.
If you want to run 6V6 in AB2 you have to drop to well down - typically A-A of 4k5-5K, and run the Anodes at up to 385V, on the upper limit, where most beam tetrodes produce least odd harmonic distortion.
Like this they WILL make as much as 20-25W, but don't expect to find that in many of the text books, and best to use the rare Westinghouse big anode variety.