I can't answer your first two questions, but to create apps, I would
recommend to write the main activity in Java and store all your Clojure
code in a jar file.
I use leiningen to create a jar containing my Clojure code and then I
write a Clojure class (using gen-class) as an interface between Java and
Clojure.
Copy the jar (not the uberjar) and clojure.jar to your Android project's
lib directory and you should be set.
Right now I'm having a small (test) app in the store (EpguideWidget) and
about to release a more complex app (a game) soon.
For both I used Clojure and the Leiningen method.
You can also write your app entirely in Clojure using saatvik's Neko for
compilation, but
Neko has not been updated for more than 6 months and it does some
things under the hood which I just do not understand right, so it just
costs me too much time to hassle with Neko errors.
- thomas