Hi John, you've gotten some good advice and comments from RVtravelz and Roughrider.
Newmar *might* have a rough AC wiring schematic for your Dutch Star and it's worth a call to find out. We may not need it to diagnose the issue, but it's a good thing to have...
Your EMS says you're connected to a 50 amp service because it measures ~240VAC from line to line but it looks like only 1 line is receiving a load. The water heater element, the house battery charger, and *maybe* whatever is on the 20 amp breaker you can't re-set are likely on the line showing no load.
How to proceed depends on your experience and comfort working in open electrical panels, which is dangerous and potentially fatal (disclaimer now made...).
As for the chassis 12VDC system, the failure is unlikely to be related to the AC service issue. The dash lights are often on the same fuse as tail/park lights, I'm told, to indicate the loss of chassis lights. If you have a trailer lights hookup, check the outlet and wiring (a few feet of it) for insulation abrasion, corrosion, other signs of being compromised. If you had a towed connected, take a look at its interconnect wiring, too.
Try the 'generator test' suggested by RVtravelz. If you have the same symptoms, it points us in a different direction than if all your AC problems go away.
Good luck and safe travels.
2005 Four Winds Majestic 23A
To the world you may be one person; but to one person you may be the world. - Dr Suess