• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Isolation Transformer: How to decouple chassis from circuit?

The DCR can be inferred from the VA and regulation specs. I don't see any observation which suggests it is "wrong".

> depending on which country you live in

His "flag" is Canada. His chassis *seems* to be a type which was only common in the US and Canada. (There were hot-chassis elsewhere but different details.)

The Wye/Delta details matter to the power company. At the house we get two wires 240 volts apart, center tapped. The CT is nominally tied to grounds on the power poles. But we are not supposed to rely on that. We are supposed to install and maintain a dirt-rod (or two). We rarely do. For outdoor use the system is dubious (muted by our low voltage on most plug-in gear). Inside above the cellar it matters less, and less-and-less as we move from iron to plastic plumbing.