There's nothing unusual in facet joint arthritis per se. It's common.
What's not uncommon either unfortunately is the chronic nature of the condition.
First off, a couple questions. Any pain in the leg? Secondly, did you/do you have pain bending forwards or backwards?
Thirdly, are you doing any exercises. Faithfully, every single day? I would strongly recommend our Lower Back Exercises
page. Read it carefully and thoroughly, digest it, find the exercises that suit you and do them faithfully EVERY morning before getting out of bed. Take it slowly, you're not training for the Olympics!
You've followed the general guidelines rather well, move from one form of treatment to another, the conservative first. No problem there. How about shopping around, talk to friends and family, colleagues and find another chiro. Take your X-rays and scans.
Let me know how you get on.