You indicated that your copper deficiency was only "mild". Seems kind of strange that a mild deficiency would cause such a major issue, and require IV supplementation. Still, it would seem that the copper IV would be a more conservative first step, especially if your symptoms are not severe. IViG seems to carry some significant potential side effects.

Maybe Mrs. D will come along and add some additional knowledge on why your copper might be low and how to bring it back up.