re 1: Bret Taylor addressed db queries in the video on Tornado (the video is on Facebook, but I cannot find the link). If you run more than one instance of Tornado per core and you have a decent load balancer in front of the instances, then short blocking calls to the db work just fine. If your db calls are taking a long time, then it might be better to speed up the queries with caching or query optimization before worrying about async.

I like this approach because I prefer writing app logic in a straight line instead of in callbacks. The code is easier to understand and debug.