hi Chris
sorry for a little bit late reply.
here we go
1. This is an unexpected behavior. I don't think It is theme dependent,still I will install group blog with cb to test this.Please let me know what Mariusooms, I am sure he will be able to point to the issue correctly(Otherwise I am always there to investigate it :) )
2. Are you using MrMaz's plugin(That is one of the awesome plugin for BP :)). I will advise you to copy the templates to either the parent/child, both will work. If you are working on multiple child themes, then put it in the parent theme.
3. Mostly child theme is known for giving you the functionality to edit css(well way back, when child theme was introduced only css files and functions.php file was allowed). Now with time, wordpress child theme has grown, and you may see now you can override anything, be it the template file or the css.
When you only want to use the main themes layout and use your own customization, better do not import the css files, just copy paste the css/images. But if you want to reuse some parent themes css, import those specific files from parent.
Specifically for cosmic buddy, I will advise you to copy the css in the child theme and start editing,as the css was not done to separate layout/design. So the other way will be easy.
and thanks for being all "buddydev", I am glad :) , I will be always here to assist you, just drop a line here.
It is not difficult to combine the top navigation with the admin bar, just point me to a screen shot, how you want it to look like, I will put a file here for you :)
P.S. If you are posting in PST, I will get back to you instantly but I may not be available to assist you instantly in other timezone(though I try my best to be here all the time :) )