Do you think there is any point in taking magnesium at this stage? I have continued with it separate from the iodine.

I don't typically recommend magnesium supplementation anymore. I find that it is somewhat overrated. Epsom salt baths are better way to get more magnesium. I would just take regular Epsom salt baths instead. But you can continue taking magnesium if you really want. If you feel that it helps you, then just keep taking it.