When I was in my late 30's I had a problem with sciatica, though standing actually made it worse than sitting did. I never did find out the cause and thankfully it's never returned. It sounds like so many things are affected by whatever the root of your problem is that it might be challenging to figure out the cause. Hoping you can find relief soon, is your chiro performing ART (active release techniques)? If not, it might be helpful to see someone who specializes in that if you want to stick with a chiro. Good luck and I hope you find relief soon!