I’m answering to the best of my ability, as far as I knew bbpress was a seperate project, like MU was. But after looking it is a plugin
Simply install bbpress into a directory on your web server. and add a link to the forum in your wordpress site menu. Do you need help installing bbpress?
The only thing I can think of is Nicer Permalinks https://bbpress.org/plugins/topic/nicer-permalinks/ its not exactly what you are looking for but its the next best thing
This is a bug with the plugin, the plugin doesn’t expect the /forum to be there so it adds its own, causing a conflict with the site. Maybe contacting the plugin creator and telling him about this bug will help.
This problem is in the theme, some code is causing it to be repeated several times. I could give better help if I could see the source code to the theme
This is a problem with the theme, simply modifying some code in your theme should fix it.
BBpress isn’t a wordpress plugin, however if installed on the same website as wordpress you can share users. Maybe I can help you setup bbpress properly?
Whats the URL to your bbpress site? Is your htaccess file writable? Have you tried adding a trailing / to your profile url?
