You can try this herb in addition to the iodine
And illite Green Clay
supplementation, as opposed to bentonite.
A lot of the common magnesium forms on the market like sulfate/epsom, citrate, oxide, are gut irritants. You probably want to switch to glycinate or orotate.
Buffered C might work, or not. You could try to get C from foods.
Fibro- your liver is definitely out, so you will need to address that at some point if you ever want to have clean blood or lymph. Temporarily you could try kombucha which some fibronauts claim helps with nodule pain, or some hyaluronic acid supplementation.
When you say 'feeling low' I'll take a stab that you mean it feels like you're more tired or maybe feel like low blood sugar. This makes sense with a fibro person starting out on Iodine
because it's going to speed up your already impaired metabolism, plus your liver is out so your ability to store glycogen is impaired. Coffee on top of this will make things even worse unless you do coffee the right way which is to drink it with protein and fat and sugar.
Actually taking magnesium on top of Iodine
and coffee could knock out your thyroid further by spinning the gears too fast and taking your adrenals out, even though you might need magnesium. It all has to be done in a balanced and slow enough time table that you don't set yourself backward.
I would look into adrenal support/diet first before you even go further with the iodine. Don't take salt with water. Take salt with foods, and then drink fluids later. This sounds ocd and weird but Dr. Batmanghelidj recommended this and I think there's something to it. In ayurveda drinking salt water is used to clean out the gut so it's the last thing you want to do when you have anything like dysentary going on.
You can also look into taking a low dose natural thyroid supplement in addition to iodine. Supplementing Iodine
does not guarantee you will have proper thyroxin production/conversion. It will most likely help a LOT in the long term, maybe even solve the problem, but starting out you want to give yourself every advantage.
Are you taking selenium? I am recommending brewer's yeast as the preferred form, not pills. Brazil nuts are good too.
As a baseline diet look at ayurveda.
Take your body temp a few times a day with the long term goal of attaining 98.6 or slightly over.