Yeah sure thing, I appreciate your meticulous engineering approach to getting to the bottom of things, it's refreshing. Good luck on future tests!
Also you asked about acoustics in the video. I'm no expert, but I picked up these two books which seem to be highly recommended as foundational to modern sound stuff:
Music, Physics, and Engineering by Harry F. Olson
Acoustics by Leo L. Beranek
I quite like them so far and have found them informative. Opening up Beranek and discovering that they treated waves in the complex exponential notation was a pleasant surprise. The main thing they don't have, at least that I'm aware of, is a treatment of Thiele-Small parameters and the (somewhat) contemporary box tuning approaches based on well-known filter circuits.
Depending on how into the weeds you're getting with tube testing, a good comprehensive book on them would be:
Theory and Applications of Electron Tubes by Reich
If you ever wanted series expansions of plate current, well Reich has 'em.