I agree with you that it appears to be starving for fuel. I'm not familiar with your set-up but I can give you some food for thought and explain the fuel system delivery on my 345 MH in case it might help.
My Onan gets fuel from same tank the MH uses, however the pick-up tube only goes about 1/2 way down inside with the intent that you can't run your tank dry while using the gen out in the boonies.
Also,on mine, the fuel pump 12V
is tied in to the oil pressure switch so in event of loss of oil pressure, or even low oil, the 12V
feed is cut off to the pump.
Hope this helps. Let us know what you find.