Golly, that's great news about your progress. You totally deserve every good thing that is happening right now.
Had a few idle thoughts to throw out, and you can see if anything fits.
Janie on Stopthethyroidmadness has written quite a bit about low ferritin being the devil to overcome. Possibly you're taking iron only long enough to feel better and not be overtly anemic, but building up your ferritin stores takes a lot longer. Weston-Price recommends ferritin of 100, and I think Janie mentions a minimum of 70 to support thyroid function.
I wonder if your "worry" is my "anxiety." I feel my anxiety ramp up when my temp is dropping or just staying low all day, and the adrenals kick into gear to support anything I'm trying to do. For me, adrenalin = anxiety. Also relates to blood sugar being wobbly. All connected. In addition to supporting thyroid and adrenals, I've found the DHA component of fish oil to be very stabilizing. I use a supplement that maximizes DHA with just a little EPA.
When you mentioned switching to Lugol's for breast pain, I'm with you on that. But I still need SSKI to partner with the Lugol's (Iodoral for me). Lugol's is heavy/dark, SSKI is light. I really like them together.
Yes, take the sublingual B12 in addition to your B complex. B complex usually has only a very small amount of B12, not enough to handle building stores of it. The methylcobalamin form is generally better absorbed than cyanocobalamin, in my experience. As Trapper is underscoring with his suggestions of B12 injections, B12 can be hard to absorb. Sublingual use helps overcome this. Or, if you want to swallow it, just use more of it to overcome the problem. I use 3 mg (3000 mcg) myself that way, which appears to be my minimum to keep back spasms at bay. DH requires 10 mg methylcobalamin and 6 mg adenosylcobalamin every day to help his defective methylation cycle (in addition to the 5-MTHF form of folic acid, the P5P form of B6, and TMG, but that's another story). He's way on the other end of the spectrum, of course, but just showing the wide range of safety, when you need it.
Oh boy, vit D is controversy itself, agreed. Individuality clearly plays a role in this. Again, DH is one example. He does hour-long runs in full sun whenever he can. He absolutely craves sunlight. He took 2000 iu vit D in addition to these runs during the summertime, in Texas, and we thought we were being very daring to add on another 1000 iu during the winter. We finally tested him one year at the end of August, when he couldn't have been more sun-sufficient. He was barely into the lowest range of vit D. And we've been supplementing more strongly ever since, year-round.
So in my opinion, should you take your cod liver oil? Absolutely. As long as it feels right to you. At some point when you feel most vit D sufficient, you might consider getting tested to put your mind to rest about combining summer sun and cod liver oil.
Genetics. We learned about this defect when he became toxic after two days of selenium. Thanks to Newport for sorting this out for us. There is also an enormous need for thiamin (B1), to forestall what's known as alcohol dementia. Thanks to DH's mother, who just died of it. On DH's maternal side, everybody ends up demented. They live long and die awful. DH is 64. I'm fighting like heck to be his ace in the hole.
I'm so glad you bring up vit A. Back in the day, it made a world of difference to my own hemorrhaging. So many things to balance. Mother Nature absolutely astonishes me.