Yep, all this, 100%.
I would add that my personal packaging preference (both sending and receiving) is to have bubble wrap around the books and packing peanuts between the wrapped book and the box. You should be able to drop the box on one of its corners (the weakest and most easily damaged spot) and not harm the book. To me that's the mark of a successfully wrapped package. If you do this then you shouldn't have to worry about the extended travel time of USPS Media Mail. As to where to get packing peanuts, I don't know the best place. UPS and FedEx stores are too expensive, IMO. I have a garbage bag that I constantly replenish from my book purchases and use for packing when I sell...