Power Steering Pump/Control Valve Questions

I have been aware that the P/S pump on our '78 has been making a few squealing/groaning noises on occasions when "under load" and warm. During our recent 1385 mile trip to the south of France in 30+ degree C heat it was doing so quite a lot! I also get the impression sometimes that the P?S is not giving me the assistance that it maybe should be.

I'm now wondering if maybe a rebuild or replacement of the pump is on the cards. But a few questions first:

Is it likely that the pump would in fact not be actually pumping enough to give it's full potential?

Would a rebuild with a "normal" kit solve that?

Could my perception of a lack of assistance be down to the Control Valve maybe? I rebuilt that some years ago, and it seemed all good then!

I should say that I have eliminated the belts as the origin of the noise and, I am not thinking at all about installing a Borganson system.

There are no leaks in the system and the fluid (I use ATF) is at the correct level.

Any thoughts and/or suggestions most welcome!😄