There is a good chance that you have some form of debris in the clutch facing of the compresser. It maybe dirt, grime, rust, or any number of things. You can try using an air compresser to blow out the clutch surfaces and if that doesn't help then you can have it looked at. You just do not have enough grip to not slip when the compresser kicks in and you accelerate. It might even correct itself before you get it into the shop by just "rubbing" itself clean when ever the compresser kicks in and the clutch clamps down on the plate. I would recomend using it more often just to clean the surface and keep rust out. The other possibility is the serpentine belt is slipping and under the extra load of the a/c is causing it to slip which would also explain the diminished power steering. Check the belt to see if its worn looking or has any dirt or oil or anything on it. The belt is easy to change, just a bit cramped under hood to work on it.