100ug of B12 is too low a dose for someone whose levels are too low and need to go up substantially. And I would guess the B12 is cyanocobalamin. In order to raise your B12 you need 1000ug of B12, and most of us do better with methylcobalamin rather than the cyano B12.
Calcium should not be supplemented unless you have been tested and been confirmed to be deficient.
Vitamin D supplementation increases calcium absorption from food. I would say that your vitamin D levels are pretty good just now. You may want to go on a maintenance dose of 1000 iU or 2000 iU vitamin D3 per day when the clocks change. Vit D is easily available from Amazon, it doesn't have to be prescribed.
Because vitamin D increases calcium absorption you have to take other supplements to make sure the calcium goes into your bones rather than your arteries. For this you need to supplement with vitamin K2. See the Mercola website for info on this. Another important supplement to go with Vitamins D3 and K2 is magnesium. There are lots of posts about magnesium on the forum, so please do a search.
Iron supplements must be taken at least 4 hours away from thyroid meds. So should vitamin D.
Rather than jumping straight from levo to T3 only, many people actually do well on a combination of levo and T3. There are a couple of options :
1) Reduce your levo by 25mcg and add 10mcg T3.
2) Leave your levo dose as it is and add 10mcg T3.
Obviously you would alter the proportions of the two meds depending on how well you get on.
Bear in mind that adding T3 to your levo may well reduce your TSH a lot, and if you are relying on your GP for meds and tests then he/she may well take fright and probably try to reduce your levo a lot.