My best guess is that the IVIG is really starting to work for you; to that I say I am so happy for you. It is not unusual to be able to stretch out the time in between treatments as time goes by. I had/have a very severe case of CIDP & 8 months of twice weekly IVIG, PP treatments, & steroid infusions did nothing for me, so just be happy that the IVIG works for you. As for the supplements, as long as yu are not paying for them & they are not hurting you, take them.
There was another young man a few years ago from New York who also came on here a feww years ago & was trying them & swearing by them. But then he came back & admitted that they did not really work in the end. I can’t remember his name, but he was 18. I wonder what ever happened to him? Anyways, I am glad that you are doing so well with this illness, best of luck!