This is a nice analysis. Looks like T100 is the way to go based on the description, in the Pacific (not GG)
Having used the T100 for around a decade (in the KR VA350i) as an amplifier tube, I can confirm that it is a beefy yet transparent sounding tube. I am curious though how it is being used here as an output tube without an output transformer as it has a quite high impedance compared to the other tubes compared. With this tube in that configuration it might be hard to match it properly to the rest of the chain. Or is it being used as a cathode follower, which would give a significantly lower output impedance. I know that the 300B can be lowered through the right choice of operating point to around 1Kohm, which is tolerable but a big transmitter tube usually starts around 10Kohm...