Is it? While assisted alighting etc. is a commonplace exemption determined by individual councils, I'm not certain it's statutory.
OP, why don't you start your challenge by simply setting out the events as regards you parking, your passenger, their condition etc. Then argue your case.
On this point, just stand back and think about this:
'..he has lived there for 60 years, they just made it permit only from 10am-11am to stop people leaving cars there and going to work on the tube. Now its silly things like this residents are being punished for.'.
?
In order for you to be able to park there must be kerbside space which there wouldn't be if the road was full of commuters' cars. Therefore all residents, your father included, benefit from access being created.
Don't knock it.
You got a PCN pure and simply because the vigilant CEO had no idea of your situation and prima facie you were parked in contravention. Frankly, even if they saw the clock or even the outline of a BB in the footwell there's no reason for them to suppose anything: issue a PCN as required and if the driver had proper cause to park there then that's an end to matters after they've explained this to the authority.
I would temper your reps accordingly. The fault, if any, is not your father's, the authority's or the CEO's..it's yours.