Ok. Start with 400mg and see how your body reacts. Maybe you'll need more, but minimum is 400mg for Iodine protocol.
Also, don't forget about the zinc. Either stop the zinc or add copper. Maybe both: reduce to 25mg zinc + 2mg chelated copper.
This of course doesn't apply if you're taking the 50mg zinc daily under a professional ND/MD/Lac/OD/Kinesiologist prescription. Then there might be a reason for it.