Who did you report it too? What did it do?
I would remove the circling root immediately (just cut off at the base without repotting) unless it's a really major one. If that's the case you may have to do it gradually over a couple of repots. I don't know why the tree is declining in vigour because I don't know how you repotted it but no doubt that has something to do with it.
I repotted about 20 cedar last month. They were in the pots about 4 years. When you need to remove quite a lot of roots or say reduce the root ball by half, I find it's best to use a smaller container so there's just enough room for the roots to fit in with about 1 inch of room all around at the most. They don't have fibrous roots and they can be left without repotting for years as long as it was done correctly in the first place.
As for shaping, there are many options but just keep in mind that cedars are not pine trees and don't grow like them. Most importantly, mature trees have flat tops and branches and this should be reflected in the shaping.
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