[annapurna]

Would you agree that one year of conservative treatments which yield no relief is enough time before pulling the surgery trigger?
I would say that this is the wrong way to ask the question. One week of conservative care with a quickly degenerating spine that is damaged in a way that conservative care can't reverse is too long. Look at how quickly you're degenerating and how much of your life you're losing. Basically, pile up the risk and benefit columns and don't worry about specific timelines. Try conservative techniques that sound promising but ask how quickly you should expect to feel a difference. Hold them to that and be the critical decision maker when you think about what you want to do.

Do you think the broad-based central disk herniation impinging upon the ventral thecal sac alone can cause sciatica?
Can it, yes. Is it likely, you'd have to look at the dermatome map and ask yourself if the pain you're feeling matches. Also, understand that a spasming muscle in area one can pinch a nerve leading to area two and make it feel like area two is the origin of the pain.

Am I correct in assuming there really isn't a lumbar ADR in existence yet which wouldn't be terribly traumatic to revise if necessary?
I believe you to be correct. If you're worried about revision, that's all the more reason to think about your idea of microdisectomy or conservative care. The investigational stuff are things you'll have to hunt down on your own, beyond what standard care within the US will offer. You can ask your doc but don't be surprised if he disparages it or is unaware of it.