I totally agree with what you say about tube amps it is such a complex topic! And I totally agree with the acoustic treatment. The best is a dedicated audio room with ceiling, back wall, window, floor treatment with some damping or diffusion materials but how many of us can afford the time and aesthetic flexibility haha! I currently listen in an untreated living room but because im usually in the direct sound field all that reverb doesn't bother me much. Not optimal though i have to say.
Im not sure about driving it at a certain volume to get tube sound, I think as long as its run through a valve tube amplifier you will get that warm tube-ish sound already. if im not wrong having some headroom and not driving the amp too hard is preferable then running the tube amp to the edges of its capacity..