Any time you post lab results, you should post the normal ranges because every lab has a different range. Clearly “<” means that it's too low for the lab to measure. Do I understand you correctly that your labs were better on the methimazole, but you had to stop because of the hives? And now you have a rash on the PTU that they're treating with steroids? You poor girl!
I have read posts online of people who had some issues (rash, etc) when they first began taking anti-thyroid meds, but they stuck with the meds and the issues eventually went away. I think they were treated with benadryl in the meantime. It might be something to ask your endo about.
That's interesting about your CT scan. Did your endo explain the reason for the delay? Is it because the iodine increased your hyperthyroidism? (I know they prefer you to be euthyroid before surgery). I'd never thought about the contrast containing iodine, but I actually had a few CT scans in the year before my Graves' was diagnosed, and I was also experiencing symptoms in that year.
I actually know someone (she used to come to my Graves' support group) who had allergies to both methimazole and PTU and needed to have a thyroidectomy even though she wasn't euthyroid. It's not ideal, but there are other things they can do to compensate. One thing that they prescribed for her (and my surgeon did for me as well - says she prescribes it for all her Graves' patients) is potassium iodide drops (brand names SSKI or Lugol's Solution) to be taken for only 10 days before the surgery. They decrease the vascularity of the thyroid. The last I heard, this woman was doing really well - maybe why she isn't coming to meetings any more.
Have you been prescribed a beta blocker? That's one thing that might help with the anxiety while you're waiting for your new dose of PTU to take effect. I think propranol is most commonly prescribed to new Graves' patients, but when I was diagnosed, I was already taking metoprolol so my doctor just increased my dose.
I don't think it's necessarily a bad thing that you have to wait 2-3 months for a definitive treatment. That will give you time to really consider both options. It's a big decision. I only know about RAI from what I've read and heard from others. I can definitely answer your questions (from my experience) about thryoidectomy.