Re: Sidebar Widgets
I asked a very similar question related to putting widgets in the sidebar with the Activity stream as the home page, rather than the blog as the home page. I got a very helpful answer from @pcwriter. You can read my question and the answer at this post: https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/can-you-customize-the-activity-stream-page/
Not sure if that answers your question specfically, but maybe it will help.