We don't know that. If you're feeling charitable you could believe they're being honest, but if you not then you just have to wonder. There is no way Facebook could prove they don't have a secret server with your data on it somewhere. Proving that would be impossible.
It definitely is a large, and more importantly external, dependency though. However, if you control the installation environment of your software this isn't really a problem. For all use cases where I had to generate pdfs this was the case (webapps and local one off scripts).
Try this instead.
Not a hundred million. Not by orders of magnitude.
There is no "other side of the story" here.
Please: do not animate things like that. Animation can be good when triggered by user interactions, to signify state transitions, but simple gratuitous animations can be quite annoying.
That's because the right people are getting their palms greased
As for 3d, i think its comfort is for the next generation of movie goers to decide on.