Re: steering cable
So, you can move the motor left and right when the cable is disconnected, but not when you connect it to the steering system.
If you cannot move the steering with the motor disconnected from the steering system, then you have a problem in the steering system. Either something broke loose under the dash, or you have a lot of drag in the cable.
I'd troubleshoot by leaving the system disconnected, then taking a bolt or whatever will give you some leverage on that cable end, and see if you can get it to move at all. If it doesn't move at all, then see if the steering wheel will move at all. If the cable has some slack, but the wheel won't move, then you may have a problem in the steering gearing.
It all depends on what you have for steering exactly as to whether you can service the whole thing or not.