Well now its time to tell what I have learned.
I have been away for a few weeks, with greeting our first grandchild, in Paris, France.
I identified what I had thought was a shunt, after getting the circuit diagram from Loren at Bend, as a 250Amp fuse, between the battery isolator and the solenoid that activates/deactivates coach power. Despite getting a voltage reading of 5 volts across the fuse, it was indeed blown. Replaced it and now the switch at the front works to shut off the coach power, just like it should! I now have an extra switch in the bedroom that does the same job.
I don't know why that fuse blew, as none of the wiring I could see looked bad, and everything but the things I have identified here worked properly. I will be keeping an eye on that one, and I will also carry a spare.
The wiring diagram also discloses that the solar panels are not connected to the chassis batteries, unless the combining solenoid is engaged, so the only charging that gets to the chassis batteries is from the alternator, or if you have a functional echo charger, which I did not have. I now have a smart charger dedicated to the chassis batteries, that is plugged into the coach AC, so is active whenever the coach is plugged in. I also now have a disconnect attached to the chassis batteries between the negative post and the grounding cables, so I can cut all loads off if I am going to be leaving the coach unattended and not plugged in. I understand from another thread that the ECM may need to be connected in cold weather, just to keep it from getting condensation damage.
I am optimistic that I have now sorted out the electrical gremlins and I can go on to other issues.