Again ... great job on maison.com - it's a thing of beauty.
Should you update the first post reflecting what you are using ?
Maybe the reasons why you are using your new method vs. the one outlined here ?
The site and the forums are on the same server, so there is no remote stuff needed. Also, I wasn't sure if we'd use xF or another system so an all-in-one connector seemed like a good idea. Now that we use xF and don't plan to change, having a versatile connector isn't that critical so I ended up putting directly the xF stuff (very light: user info retrieval, thread and post info retrieval, thread posting, thread editing) inside the codebase.
I should also point that I only load xF on the pages where I need it, not systematically.
It would be nice with some examples of that as well if not that is too much trouble.
I'm also having trouble getting the isloggedin() to work, even when I'm logged in it only returns "0", you do mention that my site need access to the forum cookies but how?
By default, XF cookies are stored for the entire domain, so a site in root is able to access cookies stored by an XF install located in /forums... Anyway, you can ensure that by editing your library/config.php file and inserting:
$config['cookie']['path'] = '/'; //the cookie is accessible in every folder
$config['cookie']['domain'] = ''; //the cookie is accessible in every subdomain