Difficult to answer, not knowing your ops manual, but:
1) C/crew NORMALLY have 1 hour extra available FDP over flight crew.
2) If I understand your post to mean that the Captain is exercising 2 hour's discretion for
flight deck, he is therefore exercising only 1 hour for c/crew. If, however, you 'lose' 30 minutes at report as you state (seems odd!), you will therefore be technically 1:30 into discretion.
Still 'legal', as, incidentally, is 3 hours discretion exercised before or during the last sector, this making your '2:30' discretion legal (in UK).
therefore we are short on hours which inevitably means we go into discretion.
- if this is true, you need to notify your regulatory authority. It is not allowed.