In the RSS export settings there is no way to export new posts in certain forums. You can do it to some extent by sorting the rss feed by topic last post. Even then it will just display the first post from the topic and link to the first page, and it would not display all posts. It's considered more of a "random" feed by followers.

Permissions checks should be done the same way I suggest here: (Hidden topics and posts should of course not be exported either.)

Same query here. I had like RSS feed to include link that at least points to the last unread post. Also, it should contain the content of the latest post in the thread. Right now, it is just annoying for users as it shows the same repeated content and links to the first page of the thread.