Regarding #1 my advise is to not use the permissions links built in to forums but instead use the interface that is available from the sitemap (if you want to control permissions on forum instances OR on the individual forum level) or from example.com/admin/applications/permissions (if you want control just over the entire instance).
In order to avoid the behaviour you describe my guess is you'll want to grant "registered users" (or some other party) the standard "create" and "write" privileges on the forum or forum instance.
"forum_moderate" is not available from the general interfaces and "write" is not available from the forums specific interface so it's basically a total mess. But it is at least possible to work around it until someone hopefully gets around to fix it.
