TRAIL GATOR Tow Bar Receiver Kit

Do I also need to buy the Seatpost Kit and the Tow Bar Receiver Kit? or they are all included?

can it be used when child is not on the bike? because i want to use it to pick up my boy from school.

Has anyone used this to tow from an adult "fatbike" (4" wide back tire) ? Would it rub when not towing?

is it easy to pack? I wanted to take on holiday so want to know if it folds up or anything