Re: external bbpress + buddypress
It’s not as simple as that. One thing you will need to tackle is getting bbPress and BuddyPress sharing the same cookies for user authentication. You need to select the ‘use existing install’ option on the BuddyPress admin to configure BuddyPress; if you have previously selected the new install option, I don’t know what the impact will be if you then tell it to use an existing install.
What you need to do is find a tutorial or guide for how to install BuddyPress forums (previous to version 1.1, you had to do it manually and it was very complicated). You could start by reading backwards on https://buddypress.org/forums/topic/forum-install-some-helping-hints-2
