Here is another thought. Good to check the column out like you are doing and if it is still stiff, there could be a problem in the power steering box hydraulic valve control causing hydraulic lock. There may be a leaking seal or O ring problem inside the valve. When you turn it one way, the oil from the other side has to go back to the pump. So every time you turn the wheel, oil for the opposite side returns to the pump. This is done in the box valve. The squeal you hear when you reach the steering stop is the relief valve in the pressure system opening to allow the oil to bypass. Since it squeals, that means the pump is putting up pressure so not likely a pump problem. The pump is always pumping oil so the relief valve opens when there is no demand for oil to move the gear box. However, many cars squeal like that at the stop. I think you may have a sticky relief valve or oil bypassing inside the control valve on the gear box which will create pressure on both sides of the control valve rather than at one side at a time. This is called hydraulic locking. You cannot have pressure on both side at the same time and be able to move it easily, but you can still move it. Would be kind of like trying to steer power steering with the motor off, very hard to turn. If it has been sitting a long time this is very possible. The parts are cheap and likely a bit of labour can cure the problem. A gear box seal and gasket set should have those parts all in the kit.