It counts your inventory and the inventory of the car you are currently in, so load up the car, grab the rest, get in and the mission will complete.

With an inserter of some sort, generally standard or long, depending on how the belts are laid out.

Which affects startup time but not throughput. It takes a little longer to get production running at full speed because it takes longer to load materials and to retrieve them, but once its running you still get the same quantity of output in the same time.