[curtis73]

Its fine to pump them up a little, but that's not what's causing the problem.

All of these problems are linked. First, of all, my guess is that your power steering pump is failing; a common ford problem. When you try to turn the steering wheel a slow speeds or stopped, the pump is straining. It doesn't provide much assist and bogs down the engine as well. Hence the low RPMs and the tough steering. The low RPMs are also causing the lights to dim because you're also slowing down the alternator causing the voltage drop.

Its also possible but inlikely that the power assist valve is faulty. There is a valve that senses when you turn the wheel and sends pressure to the proper place in the power assist box. If its not operating properly, it wouldn't send the proper fluid.

When you speed up, almost no power assist is required so the problem doesn't show up. A non-power steering car and a power steering car act almost identical at faster speeds since you don't need it then.