WOW Ben,
That machine wass really caked with residue. I have never seen one of those filters to ever look that bad. I am told that Charlotte has pretty decent water, but each of the filters I've seen have been clean, and their original color, even recently. I can see why you'd be annoyed by this one though, for sure.
The rusty tub edges are a common thing in these reverse-curl tubs. They debuted in both standard and large capacity machines with the baseplate re-design in later 1981, and I've had a love/hate relationship with them. They are great because you can hook the tub ring clips to them anywhere...they fit even on areas on the tub ring where there isn't a special notch, so if a section is badly rusted, just skip it and put two clips on either side of the rust instead. They suck because the foam tub ring gasket retains moisture, and eventually just promotes rust. I don't think I documented it in pictures, but I have "rebuilt" those edges in a few machines with two part epoxy putty so they won't leak and so the tub ring gasket has a surface to rest on. If you use the putty with wet fingers it molds like pottery clay and can be made smooth and almost like an uninterupted surface from the original tub.
From what I can see, your centerpost looks great! I don't know about the seals, but if there is no sign of detergent residue way up in the agitator, and there is no black grease splattered inside it, you're doing great.
I said it before, but COOL MACHINE!
Gordon