1) Yes you can run the fridge on while driving but make sure its on Auto or Propane setting. As others have said turn it on a few days before leaving and stock it with COLD food from your houses refrigerator. Do not put room temp food in it. Absorption refrigerators take a very long time to cool down so you do not want to waste internal coolness. I've driven for 5 hours and when parked and set up items in fridge were still cold or frozen.
2) Empty Black tank when it is full and the more liquid in it the better as far as it draining. If your on hookups use plenty of water to flush, more than you think is necessary. Some trailers come with Black tank flush fittings which is basically jusy like a sprinkler inside the tank. I do not ever leave my full between trips. It is not a septic system, just a holding tank.
3) The Generator will power all the 120v outlets, interior and exterior 120v lights, Air Conditioning and Microwave. Yes it will charge your house batteries which power all the 12V lights, refrigerator, heater, water pump.
4) One tip I like for Toy Hauler use is to get a battery powered leaf blower. Nothing cleans house like dropping the tail and blwoing out the inside. Also I have a spare set of scissor jacks for holding up the droor to make it into a patio.
5) No personal experience with WW.
