Question: Where is the director's commentary on these movies? I've looked several times on YouTube, but no luck.
Question: How much material was added for Peter Jackson's Hobbit movies that wasn't in the original novel?
Answer: Quite a bit, though much of what was added was alluded to in the film as being done elsewhere, especially scenes with Gandalf. This was likely to pad the length, as the book is rather short (around a quarter the length of the Lord of the Rings). Galadriel, Radagast, Saruman, and the Necromancer are not seen in the books, though Radagast and the Necormancer mentioned. Azog is already dead by this time. Tauriel is a new character. Legolas is never mentioned, but as Mirkwood is his home, he was likely there. Dain Ironfoot is mentioned as there, but isn't seen doing anything except taking kingship after the death of Thorin. The White Council scene is also mentioned but not seen.
Answer: Directors commentary would be on the Extended Editions of the films, not the Theatrical releases.