i think the subject line says it but i want to use the S95 like a camcorder and see the live viewfinder feed on a laptop connected via USB and then determine when to start/stop shooting.
No. There is some preliminary/experimental code to do live view over USB, but the only client software that supports this is windows only. See this thread http://chdk.setepontos.com/index.php?topic=4338.585
If you have video in capability on your mac, you could probably use that to see the display and control the camera via CHDKs PTP extension, but at a minimum you'd still have to build one of the client applications from source. Someone told me in IRC they did get ptpcam to work on a mac, so it should be possible.
Is this possible with CHDK? and is there a page that just lists what you can do with the S95 CHDK? - just a simple feature list..
There is no such thing. In general, most features are supported on all cameras, but each port has it's own individual quirks. The manual http://chdk.wikia.com/wiki/CHDK_User_Manual
covers most of the important features.