popay
1. The flight is considered to be dispatched when the aircraft is moved either under its own power or by pushback by a tug.
2. The fuel planning minima applies until the aircraft has dispatched. Once dispatched if there are problems with fuel you go back and refuel. If in flight and a fuel check reveals that the fuel on board does not meet the planning minima then it is permissable to carry out an inflight re-plan subject to conditions laid out in your ops manual. The same is true of weather minima.
3. If I had no computer fuel plan I would use the performance tables and using the current available wind charts apply a sensible (generous) factor to arrive at a suitable flight time and fuel load.
4. Yes, but my roster has to be published in accordance with FDP limitations as well.
You may be getting confused. The commanders discretion is applied on what actually happens not on what was PLANNED to happen. The planned to happen is what is on your roster, you turn up and then decide whether to use discretion based on what actually happens. You may have to use discretion due to stronger winds makeing the flight time longer than the schedule or a technical delay or a delayed inbound flight due to him suffering from stronger winds. The "PLANNED" expression used in relation to commanders discretion is completely different to the pre-flight PLANNING that you refer to in your later posts.
With regards to your comment about a captain facing charges; the commanders discretion has a maximum limit of 3 hours (with certain provisos) so if a captain planned to go over 3 hours then he could find himself in trouble He also has to take into account what the crew have been doing in their previous duties before he can decide to use discretion. If he disregarded tiring duties they have done and still went into discretion then he may also find himself in trouble with the authorities.