I cannot remember the exact time in the book Sam becomes 'Sam the Slayer' but it's after the Battle of the Fist of the First Men right? Have they completely skipped that battle!?
And if I remember correctly Sam DID let the ravens loose in the books. Not quite sure where they are going with this.
Yes, yes and yes. They did the low budget thing by skipping the battle entirely. The Battle of the Fist of the First Men is such an epic battle, hell, the name alone is epic. Also, from the little we did see, the Nights Watch kinda just stood around chilling, it didn't look like they had just been assaulted by an army of mythical monsters from the ancient past.