Not sure the exact # of season ticket holders, but there were fewer than 125 seats in the lower bowl remaining before single tickets went on sale in September. So I assume there won't be many lower bowl seats left for Memorial Cup packages on Dec 5th. But if you go on ticket atlantic right away, you should get a couple in a good spot. You can pick your exact seats on there for regular season games using their interactive seating chart, so hopefully you'll be able to do that for Memorial Cup packages as well.
The Moose shoot towards the north end of the rink in the 1st and 3rd. That is, if you're in section 8, the Moose are shooting to your right.
You can't really go wrong with the food/drinks downtown before the game. HFXSports will have all the sports on their billions of TVs before the Sunday game (World Hockey Championship gold medal game should be that day). Maxwells has something like 100+ beers on tap, although their food can be iffy at times. The Midtown is a good spot for a simple steak and a beer.