Number 1. It must be by credit card.

Number 2. If there are no points associated with the ticket then you can pay on line.

Number 3. If there are points then you must go to one of the police stations... Al Rayyan, Madinat Khalifa, Airport Traffic on Tadmur and E Ring or one of the kiosks at the airport and I think some of the malls.

good luck

On #3 that may only be for cars that the sponsors own, if it is your personal vehicle and your Qatar license is is tied to the vehicle then you may be able to pay on line. But company cars cannot because they don't know whom to assign the points to.