how do I fix stiff and jerky power steering?

Check the condition of your belt(s) that power your power steering pump. I am not sure if your vehicle uses a serpentine belt that runs all of accessories (a/c, water pump, power steering, etc. ) or if your truck has a separate belt for the power steering pump. If this belt is worn it may cause this issue. Also, check the fluid level in the power steering pump and make sure there are no leaks in any of the hoses that come from the power steering pump. I hope this helps!