1. Not clear on what your doing but if your editing templates and adding links or the like make sure to properly use full urls to files not relative links.
2. You cant. Usergroup permissions are not used to give different layouts.
3. Do you mean avatar? You would need to actually post a url and test login for an answer,
4. Your forum user management is where you administer users so that would be in SMF
5. You can not
6. Well what is not correct? what do you see?