Do you have any info or sources or anything I can learn more about the dosing of IVIG? I see you say it's 1000-2000mg/kg vs 400-500mg/kg.
I can't remember how my doctors calculated the exact formula back in 2016 but I know that it was based on my body weight (at that time). IVIG for autoimmunity is a much higher dose than when it is used in immune deficiency.
Also what type of doctor treated you? A neurologist or rheumatologist?
My two doctors who I worked with for IVIG were an internist and an allergist/immunologist. Sadly both of them have now retired. We tried very hard to find a neuromuscular specialist (or any neuro) to help but ultimately did not find one and proceeded without a Neuro.