Re: custom fields for posts
The easiest way to add tags with spaces is to post the topic then add tags one at a time in the top right-hand-corner of the thread (next to the post title), which are not space delimited (must be added one at a time though!).
No plugins for any of those as far as I know. BBPress is great but perhaps a solution with (currently) more features and plugins like phpBB is for you.