I'll jump in here if you don't mind...
You can set the parameters in the Victron app for the Orion DCDC converter.
Not sure what you are asking here " Is there any potential with that same charge parameter charging your starter battery? Or is that parameter gone since the power passes through the house battery?" since the DC-DC charger is one way from starter system to house system.
IF, you are asking if the Victron MPPT settings (which are customizable) will affect how the Solar MPPT system charges the starter battery via the bypass relay rando uses ... yes, they will. It will apply those parameters to all the batteries it "sees" connected to it. Since the truck battery will be some distance away over wires, it will see a less than perfect view of your starting/truck battery.
Regarding wire sizes:
A) In my system I run 2AWG welding cable
Same as above
C) Same as above
D) DC-DC charger to house batteries - 8G wire... largest I could get to fit the converter
E) The 2g cables from the truck to the camper are joined via anderson power pole connectors in the truck bed. Those run to a 100A Blue Sea 285 series breaker. From the breaker to the DC-DC converter is 8G.