1. Mormon transitions from Amaron's death farewell (O 30), which lacks the glorious and prophetic quality of Nephi's and Moroni's parallel farewells, nicely into the destruction of the Nephites in his own day. Then, since the small plates are full of teaching and prophesying about Christ, he notes that in the meantime, Christ has come, and he hopes his son Moroni will be able to write something about him.
2. This is a stark change out of the constant temple imagery of the small plates, other than the sly hint in v. 7 (a "wise purpose"). It's administrative, behind the scenes, explaining what Mormon has been up to.
3. WM 10 here again, it looks like Mosiah took with him the Nephite royal records (and in v. 13, we have the sword of Laban) (cf. 2 Nephi 5:12-14). So one guesses he was of the royal class or party of the Nephites before he fled, maybe a (more or less distant) cousin of the record-keeping branch of Nephi's descendants.
4. Interesting that plates get "delivered up" (vv. 1, 10) and "handed down" (v. 11).
5. WM 15 it seems that in Benjamin's day, whatsoever a man believed could indeed be a crime.
6. WM 16 the Lamanites might have been barbarians in tents, but there was still something attractive enough about them that they continued to attract Nephite defectors... "many dissensions". What was it? A different doctrinal preference? Maybe not everyone liked Benjamin's reforms and consolidation of power.