Since the user above managed to answer most of the questions:

2. The counter actually increases by 15 minutes and then you automatically become inactive until you refresh the page. So If you just visit a thread, go inactive for a few minutes, then refresh the page, you will see that your total time logged in increased by 15mn.

4. I don't get it either. If you mean the ability to close topics, then that's something you could do in the other sections as well.

5. You should start using the Watchlist instead of "Show new replies to your posts", which can be easily edited: https://bitcointalk.org/watchlist.php