2 - LED type 921
3 - It is the same length as the camper minus the storage box if you got it. So that is 12 feet and it comes out about the same width as the trailer width, so 7 feet.
4 - I have gone a whole weekend using the furnace (Colder nights) and had no problem. Still about 80% left on the battery.
5 - From my reading I understand that you will need a minimum 2000 watt (Honda/Yamaha) at sea level. I would say go with the 2400 watt tri-fuel Yamaha. Then you can run it off your propane tanks (20lb tank you can get up to 44 hours).
EF2400is
6 - The BBQ that comes with it in my opinion is ok. Only 10,000 btu I believe so it is enough to do hamburgers, hot dogs etc. After less than a year of use (10 camping trips) the heat deflector is almost all the way off. I have already replaced mine with a Camp Chef Pro 60 (Griddle/Pro BBQ Box) which has two 30,000 btu burners.