1. it's okay, styrofoam peanuts for bigger orders, cardboard envelopes of better quality than Amazon's for single books (i recall getting a single tpb in a bubble mailer once but it was a long time ago). if anything gets smashed in transit, they will offer replacement or a refund (50%, as a rule, it seems to be their standard nick&dent discount)
2. i backordered from them only once, an action figure, they shipped it to me three weeks later. i guess there's always a chance they won't be able to get a backorder from the supplier but i'm inclined to think that as long as the item is marked "available for backorder" and not "unavailable" or "out of stock" (which is not always a permanent thing btw), it's rather a slim chance.