3) there is a physical trigger inside of the jack that is hit when you plug in a headset. My recommendation would be getting a cheap USB sound card if you use something like Ventrilo. Game audio is harder because you don't want to switch the output back & forth. I haven't tried to do it with Windows 7 and I understand that the audio sub system is different but I used to route different audio through different sound devices.
4) map changes are independent of the GPU because only real time graphics are rendered with the GPU. It is either the CPU staying downclocked for some reason (are you running on battery?) or the hard drive.
A bus station is where a bus stops. A train station is where a train stops. On my desk, I have a work station…