My traveling is very similar to yours. Lots of driving time to charge the battery. The important thing is to make sure you have a dedicated circuit from the alternator to the camper battery, with a minimum 10 gauge, preferably 4 gauge power and ground wire. The factory plug will not do a good job keeping the house battery charged, because the alternator will sense the truck battery state of charge, not the camper battery. A big fat wire with solid connections cures that.
I decided not to splurge on the big dollar batteries, because I don't want to spend my vacation time trying to preserve it's life. I just go with a cheap $90 battery and replace it when I need to. Only your usage can tell you if 1 battery is enuff. Just try it. If you get a $90 battery, you have little risk. If it runs too low, you can start the truck and/or the generator to get you back up, then add another battery. Perhaps there is room under the hood of the truck?
