In regards to your question about server-side Dart, it seems that the space is just beginning to mature. A couple frameworks have solidified a fan base such as:

http://redstonedart.org

https://github.com/lvivski/start

There's also a Dart specific hosting service that's in beta: http://www.dartvoid.com

And there's been some success running Dart on Google Compute Engine through App Engine Managed VM (not sure if this is out of beta).