Incorrect.
They are not allowed to transmit with more than 1500 watts on any band. If they have a novice/technicians license, they are limited to no more than 200 watts on any band.
Some bands have additional power restrictions. 30 meter = 200 watts for anyone. 10 meter = 200 watt for anyone. 1.25 meter = Novice limited to 25 watt. 23cm = 5 watts for everyone. etc...

It doesn't even matter if he's following the power limitation rules if his equipment has other problems that affect nearby equipment.

You can do all the grounding and bonding you want, but if he's running a signal with distortion in it, he can be spraying spurious signals all over bands he's not tuned to.

I mean, what if he's running CW and his bug chirps?

Take a neon tube tester and go zap one of his cameras... it will probably ruin everything in his house too.

But there has been no definitive proof yet, that he is causing ANY of these problems.
This is why I stressed about getting the proper test equipment, to analyze what is going on. Like I said in my 1st post - unless he has defective equipment, bad grounding, or running an illegal amp - it is unlikely he is causing the WiFi problems.

And the zone 2 voice bleed thru, could very well be poorly designed equipment on Denon's part.

A bad connection can create a very nice AM detector.  I've had radio stations playing in speakers when the equipment was OFF.

Are you sure that the leakage to Zone2 is from the Ham? I've had the receiver's own tuner or other non selected sources bleed into the output. The only cure for tuner bleed was to tune off channel and hope that the tuner would mute. I had to assign a null station preset. Other unused sources had to be forced OFF.