1998 Mazda 626 AC causes odd symptoms

I own a '98 Mazda 626 with 130,000 miles. I'm hoping someone out there can shed some light on this situation. Its important to note that the following symptoms occur only when the AC is on and the car is in stop and go traffic. The car runs fine when the AC is not engaged or when the AC is on under highway conditions 1. Car loses approximately 5-7 hundred rpm when the AC cycles on. Is this high? 2. I live in Southern California. The summers are hot. After driving the car in stop and go traffic I'll come to a stop (at a light for instance) and the idle speed will drastically fluctuate between the normal idle speed of approximately 7-8 hundred rpm to almost 0. In other words the car will almost stall. If I turn off the AC compressor the fluctuating stops. 3. When it gets to that point, the AC will stop cooling and the car will almost overheat. Again, these symptoms occur only when the AC is on and the car is in stop and go traffic. Any help is greatly appreciated.