Good video, indeed, the text scrolls quickly at the beginning, but hey, you can always press the "pause" button on the player ...
Regarding the strange difference that you noticed between your small fluorescent bench top and the double "large model", it may be that the fluorescent tubes in tandem are mounted in phase opposition, which would create a cancellation of the EM field ...
To check it, just remove one, and see if there is a difference ...
For the microwave, it's the complete hallu!
I remember having learned, during an internship in home appliances, to manufacture a leak detector EM microwave for cheap:
You take a recovery "firefly" (you know, the lights that are found in particular in the luminous buttons of freezers, and also in the luminous switches for the lighting of the cellars) to which you cut the two feeding legs.
Then you take a piece of plastic or wood that you just drill to the right diameter to insert the light. It's ready.
If you put the thing in the microwave, and you make it work, the light should come on.
By cons, if you walk around the door (at the joints)
you must not have anything - if it lights up, it means that you have a leak of μ waves ...
Your device seems to be more sensitive than my hack, but I still wonder about the nature of what it detects ...
Indeed, it is necessary to know that a particular care is brought to the waveguide of the klystron (the machine which generates the μ waves) and to the watertightness of the speaker with respect to the μ waves (cage of Faraday) .
On the other hand, for having disassembled, I can testify that the BIG power transformer is not specially shielded, and must therefore not badly radiate, but in 50 Hz, him.
So, maybe it's him that your device detects ...
... well, all this does not especially clear the microwave, which remains in my eyes a big shit, in all points of view (and that does not come to tell me that it saves time, I tested my own methods for baking, reheating and thawing, and I can assure that I will, too, see faster than the microwave!)
Congratulations for your perseverance!