I cannot critique your rewiring but I also installed a switch to parallel the generator battery with the engine/house battery.
I also have two 8D engine/house batteries with the conventional Off, 1, 2, Both switch. The generator battery is a 4D
I installed a Blue Seas e-Series Single Circuit ON/OFF Battery Switch PN 9003e to parallel the Generator Battery to the Starboard Engine Battery.
This gives the flexibility to start the generator if its battery is weak or start an engine if its battery is weak.
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