Hypothyroidism chronically is an inflammation disease in the entire body. Sometimes it is less visable on the outside and more internal with swelling. Commonly the inflammation can grow in the ear canal and other areas that can cause a ringing in the ear. So many hypos have this but when optimal is less pronouced and tolerated.
I don't know if I have heard anyone with hypoT or Hashimoto that can say this had been cured - even being optimal - it seems once it starts its present but gets less noticable as time and healing happen balancing back out.
As for the B supplements... yes it may help or not. B's are essential to hypo patients but how much is an individual level. Its hard to overdose on a B since it is water soluable in the body and waste out what we don't need.
My feeling is more - taking the B and then something changing more thyroid hormone wise happened and you may need to see if your thyroid labs changed here.
I have Hashi's and also have that stmptom, and I have read here that other thyroid sufferers do too, I have not heard that it is caused by a lack of B, I take B and still get the ringing on and off, I hope you get a response as to the cause, because I would like to know also. Good Luck FTB4