You have answered your own question. ALL of the conditions must be satisfied & that means condition (d) must also be satisfied, i.e. the costs of the flight MUST be shared. So if you are cost sharing, the maximum number of people on the flight, including the crew, is 6. If you are not cost sharing, the entire (7A) section is not relevant & therefore there is no restriction on the maximum number of people on the flight.
Good point! I will happily retract my post!