Use custom CSS or edit the PHP. No settings at the moment.
Gareth, isn't that little circle (i.e., the "target" icon) what puts one into Single Topic view? I thought that this could be turned on and off with a Collapsed Topic setting. I haven't messed with this because I like it, and show it.
Karius, you might want to turn these features off for some good reasons. However, my students really use these features and like them, so I encourage you to leave them showing.
Yes it is and no it currently can't! ;).