Hi Johnna
Any chance of a chiropractic issue here? To guard against aggravation I always check the pulse afterward to make sure it feels better to me (more moderate, less toned).
There is always a chance that you have a standard Kidney deficiency creating the predisposition to Wind invasion. In that case, you'd need some tonifying in addition to the expulsion of the pathogen. Du Huo Ji Sheng Tang (aka Kan Essential's Supple Spine) may help you there. I would expect a response to KI 3 or BL 23 if it were to help. Kidney deficiency probably goes with the profound sedation in response to Gabapentin, too
Lastly, there is always the chance of active inflammation of the back going on, in which case concomitant use for a few days with your herbs of an NSAID may help avoid the acupuncture being irritating. Even plain old ASA may help. A 6kg cat could probably handle 80 mg ASA up to TID if necessary, for at least a little bit
Those are just some thoughts. Hopefully there is a useful idea in there somewhere
Steve