This can cause serious problems even on its own. I don't know if you are familiar with the serious side effects of this class of substances. There are many good informations in the net. I recently saw one of the leading US-experts in german TV on this topic. His name was Charles Bennett. Maybe this helps you for further research. However, I'm not sure if Levaquin can cause CFS. Mostly I hear of neuropathies and joint problems.
You cannot conclude that this is a past infection just because of low or even negative IgM. As far as I know even in most cases of Zoster reactivation with the typical blisters, the vast majority of patients are IgM negative.
It depends on how long a treatment should last according to specialists. Based on this lab results I would surely do no long term treatment like that recommended for other viruses. I think I would look for other viruses and bacteria first and then decide what to do when all lab results lie on the table.
This thread is interesting. My CFS may have started with shingles. Around the same time I got subacute thyroiditis (large, painful goiter treated with steroids). That was the start of Hashimoto's autoimmune thyroid disease. I'm not sure then what thing caused the CFS but I've suspected the shingles. But this was 22 years ago. There are periods where I feel like some kind of virus "wakes up" in me based on signs and symptoms.
I'm not sure if it can be pursued now?
While this thread is interesting a lot of it is going by me because of brain fog. Can''t comprehend vey technical things anymore.