'68 Barracuda Power Steering Gear Box Problems

Let's start at the beginning. Original steering gear (rebuilt once) worked perfectly, giving me the light fingertip steering that Mopars had back then. So the fan belt broke one day and the car overheated on the 2 mile trip home. Car drove fine after replacing the belt, but the power steering gear began to leak badly. My theory is that the overheat may have melted a seal in the gear, causing it to leak. So bought a reman gear from CarSteering.com and installed it. After bleeding and going for a test ride, the steering is so tight that it feels like almost no assist at all. Also, the steering will not re-center after a turn in either direction without me forcing it back. I have tried loosening the segment locknut and loosening the adjustment screw 3/4 turn, to no avail.
So the questions are:

Will the gear loosen up over time?

Is the amount of assist set during re-manufacturing to some "one size fits all" amount? And is it adjustable?

Is the reman unit defective?

Should I send them my original unit to re-build, or will I end up with the same stiff result?

It would seem to me that the no re-centering problem is downright dangerous! Please give me your thoughts on what to do.