[frankhond]

Thumb over technique is not a problem in itself, but tension is.

I would rather suspect the sudden change in musical repertoire you mention, with new positions, causing tension in your neck, back, arms etc.

Having played for 30 years you might be used to be able to push through any technical issues, which in this case (probably combined with climbing) created an issue. There are plenty of examples where pros suddenly develop problems, some never recover (look up oliver sacks recent book about music which includes a pianist who got dystonia).

Besides resting I would suggest practicing pretending you are a beginner, real slow and easy, taking care to remove any tensions and bad angles. Maybe you can isolate some specific issue that causes the pain.

I had a similar issue way back which basically prevented me from playing. Finally I figured out it was a wrist angle problem. But only after several years of pausing, resting, doctors, teachers etc. Eventually slowing down and being real attentive cleared a way and now I'm symptom free.

Best of luck!