"The next time it will be 10 hours, the time after that 11 hours" It can never be more that the CAD FTLs allow can it? Isn't the dispensation a dispensation between the company's filed FTLs and the CAD's maximum FTLs? I don't see it as the thin edge of a wedge, more a utilisation of the difference between what the company has agreed with it's pilots and what the CAD will allow, only to be used by the company in one-off and unforeseen circumstances, doesn't your association agreement with the company cover that?
ACMS - Call time 23.30? Be it two or three crew are you suggesting that they didn't meet for lunch and then retire until call time?
If you are going to attack the company over dispensations then I earnestly suggest you pick much stronger ground that this particular flight.