I don't have any specific answer for you. The Aqua-Rite units are better than most, apparently, but that's not saying a lot. I've never worked on them myself, so I can't really comment. I have no idea what the list of numbers you supplied are.

I will offer a few observations.
  • 3.5 years of life is unusually long for an SWCG operating year round.
  • Low salt readings may indicate cell failure.
  • It is certainly possible for a new cell to be defective. But it's also possible to damage electronics (and electrical components) putting them in a bad circuit.
  • I'd recommend you use my Super Search page to look through all the major pool forum sites for Aqua Rite troubleshooting.
  • I'd would have recommended calling Hayward, but at this point I think you've changed so much that they are likely to tell you, "You should have called a pro" . . . just because they will have no idea exactly what you've done. (Consumer self-reports of repair efforts are notoriously considered untrustworthy by customer service agents, regardless of industry.)

Good luck!