Because it's based on an incomplete tibia, so whether it's actually Alamosaurus or some other giant titanosaur isn't really an open and shut case.
We don't know for sure - there are too many missing to know the shape of the sail with any certainty right now. Mostly I wanted to push back on everyone adopting the paleoart meme of the M-shaped sail, since there's no evidence for it at this time.
I see what you did there. I do think the neural spines would sustain damage from moving beyond the normal range of the tail. But since they are almost certainly being held in by skin and connective tissue they would probably heal to some degree most of the time. This was exactly why I didn't straighten out every neural spine perfectly from the fossil condition.