My idle is only at 600 rpm, tons of vibration

Hello, Do you have a check engine light on? If the vehicle runs normally when engine speed is above idle, the chances are you have a dirty/clogged/leaking idle air control valve. There is a little port inside the throttle body, and that is connected to the idle air control valve (IACV). When they become dirty, your symptoms are replicated. The lower engine speed with A/C, heater, windows, etc, is due to extra rotational resistance on the engine, and is likely not contributing. Disconnect the battery, and remove the intake air tube to the throttle body. Look inside the throttle body. How dirty is it? Does the IACV port look corroded or clean? Lastly, make sure the throttle body and IACV gaskets are not leaking. Any luck?