General Easy Questions

Im not new to wordpress, but i am new to buddypress and multi sites.
I finall got it all up and going, now i am tweaking settings and getting an understanding about how it works, but I have some questions that I can't find answers too:

1. How do I setup a default theme for when a blog is made? I'd like to use thesis.
2. How do I setup default content for when a blog is made? Is that even possible?
3. How do I disable wp-admin items (down the left) in a users blog by default when a blog is created? For example, I only want to give them access to posts, media, links, pages, and comments. The rest I'd like to disable