Can you tell me why after radiation treatment for an over active thyroid the meds still don't work well and can't be regulated?

Hyper thyroid. Graves or overactive autoimmune thyroid disease can be difficult to control, both medically and surgically. Most docs first recommend medical therapy, which sometimes ends up with three rounds of radioactive iodine, anti thyroid meds and close monitoring with your endocrinologist. Surgery consult when you are not tolerating the medical regimen.
Not true. Medications work very well for both overactive and underactive thyroid. Problems with regulation are related to your dosing or to the adequacy of the ablation. Those should be easy to figure out.