NO, Not STEEL WOOL!
That will send dust into the electronics, then, watch out!
On the part that broke, not to worry. No replacement made, but, it was used for centering the picture tube. Why did you take everything apart?
You didn't really need to go that far. Just more work to adjust erverything when you get it running, again.
Leave those sheets of asbestos alone.
They were extra insulation against over heating cabinet, which might cause paint to blister.
They are painted inside to keep asbestos from flaking off. Also, one of those sheets has the all important tube chart on it.
I've seen worse looking sets.
I use a good grade of brass polish on the chassis'.
They were originally quite shiny.
Here, again, nor needed for correct operation.
Another worry you have is whether, or, not the large bank of resistors on the back of chassis, are, good, or, not.
I didn't used to see them bad, but, am finding more of them failing.
Usually they burn out, but, sometimes they short to chassis.
B-is not on chassis. Chassis is a 90 volts dc aove B-.
It's part of the bias supply, which is also part of that bank of resistors on the back.
A little tedious to work on, but, they perform well.
On that belt, I use a neopreme heavy O ring that I buy at the hardware store.
I have very good luck with them. Keep the original belt tension pulley. It helps against slippage.
Be very cautious on oscilator adjustments on all the RCA wafer tuners. The screws are at B+ level, and, you'd get a loud bang from shorts. Plus, at any rate, due to frequency changes, you should never use a metal tool to adjust them anyhow.
The tuners were RCA's weakest point. They were basically lousy.
But, the sets are good performers, and, show an excellent picture.