I lowered my oxalate intake--thinks: regular chard, spinach, daily nuts to keep weight on, dark chocolate, sweet potatoes--pretty drastically from one day to the next last January, so over 8 months ago. My pain levels were very high. BUT, I also was having a terrible time with all those Bs, particularly the MeB-12 and Folate levels. I spent months having daily diarrhea. In retrospect, I think this was not only oxalate dumping, but also a paradoxical folate block, which I have to a much lesser, only rarely extent now that I can (barely!) tolerate 1 mg of B-12 and 400mcg of Folate.
My brother, like you, has a fairly rapid physical response to oxalates. I can only say that keeping my diet in the low-medium range, using calcium, magnesium, lots of B6 (25-35mg p5p daily) and finally being able to tolerate B-12 has reduced my pain a LOT. What I feel now is the damage from 15 years or more of having this disorder, not the drill-bit pain with every move I take.