Send me a private message that includes your e-mail address and I'll send you a copy of the package of wiring diagrams that Monaco sent me for the 2006 Monarch (twin to our HR Admirals).
Seems to me the immediate problem is the engine dies. It may or may not be related to battery condition (chassis or house), charging interconnections or the alternator.
You say both chassis and house batteries are "good"; on what evidence do you say this? Have you tested them? If so, what were the test results? There are many posts on iRV2 telling how to test batteries. Here is a link
to the result of a Google search for iRV2 posts with the terms "battery" and "test" in them.
The fact that the engine restarts when using the "Batt Boost" switch on the dash implies:
1) The chassis battery is weak, and
2) The solenoid used to connect the chassis and house batteries for cross-charging works when manually activated
I have posted a picture of the front distribution panel with the solenoid circled in red at this link
This, and the wiring diagrams, should be enough to get you started. I expect several other iRV2 members who post often on this topic to be responding shortly.