Power steering on a 99 ford Taurus

I recently bought a 99 ford Taurus with the
knowledge that there was a power steering
problem. I replaced the steering pump and
the power steering pulley. Recently while
driving the steering wheel is extremely tight
but others wise drive fine. Until recently the
steering wheel started shaking and the car
started over heating and when I looked
under my hood the belt had come
completely off but it was not broken and my
power steering pulley was chipped. Could it
be the idler pulley or something else please
help me and also I have alot of trouble
keeping power steering fluid in the car I put
two bottles of power steering fluid in it in
one week...