Re: I might have broken the whole install…
The siteurl and home (url) are required by BuddyPress to properly determine where it needs to look to find its various support files. So, that is why you could still access BP but the layout looked funky. BP could not resolve the path to the theme’s CSS files.
If you changed the url back to the original, proper path, it all should work now without any issues. Is that the case?
I assume that you were trying to provide your friend some assistance to a different issue. If you have a new issue, unrelated to this particular topic, please start a new thread and mark this one resolved.
By the way, for future reference, the topic you posted here is a WordPress issue and not a BuddyPress issue. That’s fine that you posted here, but if you have additional problems related to this particular issue, I’d suggest posting in the WordPress forums instead as most people here ignore issues that are not BuddyPress specific. I just happened to be looking at the right time!
Of course, if you have BuddyPress-specific issues, then post them in these forums.