Their reservations seem to be seated late (as in 20-30 minutes). Every time we have gone, this has been our experience. This meal is served family style (they serve as much as you like) - just ask for more. I would say allow 75-90 minutes for eating.
You will be able to see the fireworks, but Happily Ever After has projections on the front of the castle. You won't see any of the projections.