The button isn't supposed to go all of the way in. If the green light comes on and stays on, it's likely that the foglights are burned out (can't be a fuse issue, as, when my fuse went, the green light wouldn't come on).
I'd have the pressure checked in your A/C... you definitely don't want to be running the A/C (or defrost) if it's low (images of grenaded AC compressor still vivid in my mind after 2 years - thank god for extended warranties). It could also be a problem with the "blend box" which is supposed to adjust the hot/cold air based upon your HVAC settings, but I'd start with getting the system pressure-tested and refilled (find a good automotive cooling place if you're not familiar with adding refrigerant yourself, and stay away from the dealer).