Sounds very familiar. My son had titers of 1800 and many of the symptoms you have stated above at age 8. . We saw Latimer in 2009. She recommended plasmaphoresis due to his extreme presentation and the high titers. We were back to baseline after 5 days of plasmaphoresis and I thought we left cured. Four months later he relapsed (not as severe) after a flu shot, and ultimately needed some IVIG to retrain his immune system. We too, had not had a positive strep test since 2006. For us it was clearly autoimmune.
Both azithromycin and steroids worked for us to buy some time until we could get the IVIG. They did not fix things, but allowed him to get back in school. They were a band aid for him.
He is 12 1/2 now and doing phenomenal. He had no current issues, and has not had any for years. See Latimer. She saved us.