First issue, what version of VaultWiki are you on? If you're having trouble converting an existing forum, try creating a new forum, then manually move the old threads into it.
Second issue, your wiki page should look like that automatically if you have some namespaces. You don't have any, so I can't see your current home page right now.
Third issue, yes this happens because you have custom permissions for that forum, but you have not already set custom wiki permissions for that forum. So they all default to No as a security measure.