Re: Filter activity by blog (or group)?
If you’d like to associate a blog with a group, you could use Marius Ooms’ BP Groupblog plugin:
Most likely the group filter will pick up the blog as a group.
There’s also Andy’s External Feeds plugin:
Which you can use to grab an RSS feed and it will populate the group activity and site-wide activity streams.
About the other questions, I don’t have time to delve into it!
Maybe a mod or someone else can help you.