well, if you run that query, it should show you what you did for posts and threads in that forum. As far as the postbit goes, that would have to be done completely differently as not as add a query for every post on the page of a thread.
Now, I did a hack that I haven't released here that goes in the postbit and tells you how many threads each user has started (board-wide) right next to the Posts each user has made in the postbit, but it won't break it down per forum like you want.
So, it all depends what you are wanting to do, I guess. If you want it per forum and want it in the postbit, that would have to be another new hack altogether.