Glad to hear you're feeling somewhat better, but it does sound like you're caught in a Catch 22 where you can't be 'half' fit for flying.
The only thing I can add into the mix is that I have had two patients recently who have had lumbar microdiscectomies and the results have been excellent. Much better than the lengthy grinding agony which most NHS patients have to put up with before they eventually, gradually improve.
Interestingly, the patient I saw today had the op 1 month ago and he is now fine, but his surgeon told him to wait 12 weeks before going back to work. (He is a dairy farmer, though -- slightly more strenuous than pilot!) The surgeon also told this fellow that pain-wise the evidence is that microdiscectomy patients do better up to four years post-event, by which time the conservatively treated patients catch up and are just as good. Four years, though, is a long time to have a bad back.
QDM