I'm glad Wilma got a clear bill of health.

Regarding Six'd false positive test, I haven't got direct experience but when Bramble started being sickly, we had to have her retested and my vet told me all about the tests.

From what I remember he said that it is not uncommon to get a false positive but as a vet he would look at the health of a cat.
He would recommend retesting of cats which had certain symptoms and had a positive result. If the cat was healthy and had no risky background (i.e. Living with an infected cat) he would say this is a false positive. In conclusion, don't worry from what you said Six will be clear (Fingers Crossed)

Poor Elvis, don't chew your paw it will hurt you. Can they do anything for his early cataracts ?