You can change the post.php template page to make the avatar link to the profile.
I have it so the name links there and it works fine.
<a href="/forums/profile/<?php post_author_id(); ?>"><?php post_author(); ?></a>
As for the URL not updating, this is fixed in the Trunk build, but I don’t think it’s made it to the alpha yet. See https://trac.bbpress.org/changeset/1930