VLC : you must add some gstreamer packages. Here is a good list, taken from the good Zen mini.
You can also get packages such as libdvdreadcss2, libdvdread3 and libdvdread4, libmatroska2... If you need a full version, there is a Openbox full by the way. Bonsai is a "do it yourself" version made easy. For purpose such as new version with a specific aim.
Regarding the mouse wheel, I was looking through all the included applications with your distro and I noticed FEH was listed in synaptic. So I passed it a directory to browse through via the prompt.
I can't remember the exact arguments I supplied it was a directory (not a single image) and I told it to go full screen. The mouse wheel worked when rolled away (previous image) but did not work when rolled towards me (next image).
Would you try the easy way ? In ~/.config/openbox/autostart.sh file there are 2 lines for feh, uncomment one and comment pcmanfm as a desktop manager. then restart X, and look.
I have installed it so that people have a choice for the background management. I have no idea how to use it currently.
Or there might be a doc at the website, a man...
For the keybindings, you will find a rc.xml file in /etc/xdg/openbox directory. The original configuration files are pretty hard to use, this is why I have provided all made ones. If you find good keybindings to use with A-tab, you can suggest them so I can add them to the next set of configuration files.
Just take care of not having the same feature provided by other ones, or two keybindings fighting...
About updates : this is the first thing you HAVE to do before installing any other program.