It won't be as pretty, but I deal with large data models all the time, and like to use SchemaSpy [1] which generates an interactive page in HTML and can be used on the command line (I guess you could always modify the CSS to make it pretty). It's literally one of the most useful tools in my life, and the output is good enough to show to clients.
If I'm designing a DB or even just an SQL example, I'll run the code on my local machine (psql + the Postgres app [2]) or if I'm lucky, the client already has a server running Postgres and I can run it there instead. All SchemaSpy then needs is access to the DB and voila, interactive example.
Lucidchart has the ability to generate SQL for you to run and it'll generate a schema for you. I used it to figure out the schema for a particularly poorly designed DB I had to get data out of.
No, I wish there was. Those were painstakingly drawn by hand.
Possibly DiagrammeR?
And of course, thanks for another great book, it's helpful for learning R but I'm always enlightened by how thoroughly you explain the general concepts (e.g. Relational data and joins). Have heard a few people on faculty speak enthusiastically about the book even as I hold out for more adoption of Python :)