You have post-surgical hypothyroidism, but your current thyroid dose is making you hyper (TSH <0.03). Some people gain weight with hyper -- the thought is increased appetite/food intake -- if this is not the case, I am not sure what to suggest. There is not a proven method to help this situation. A combo of T4/T3 may be worth a trial, but is not considered a "weight-loss" approach. Avoid armour as this may make the thyroglobulin dificult to interpret in cancer follow-up.
I can definitely understand what you're going through. My TT was in February and I have been gaining weight over the last 8 months relentlessly. I have been on a less than 1000 calorie a day diet ever since the TT with no avail, even though my doctor prescribed a little more thyroid medicine (for suppression as well as to help me out with the weight). Finally, this week I went to see him and he prescribed an appetite suppressant. I am not sure what that will accomplish since my caloric intake is so low anyway, but he thought I should try it out and see what happens. I read all these posts on thyroid and weight gain and so many people claim that once the medicine is at its optimal level then everything will be ok. Well, it's not that easy for everyone. Good luck and talk to your doctor.
I wonder if something unrelated to thyroid might be occuring?
I was always told if you are kept within normal thyroid levels that weight gain should not occur. For me this has held true, whether on ATD's or replacement. I had a TT in December of '04 and weigh a few pounds less than before surgery. I did gain a few post surgery. A year or so later and one Christmas binge later I found myself up about 6 lbs then totally changed the way I eat following the South Beach plan. I actually lost 11 lbs in the first 2 weeks and have leveled out at 8 lbs weight loss due to diet modification without killing myself. I follow the principal now rather than the diet exactly. I believe age, the fact that your metabolism has changed a bit and activity levels may also come into play. Looking at they types of foods that you eat rather than the caloric content is worth examining.
I'm not telling you this to rub your face in it, I'm hoping you can see that it might take a total adjustment in the way you eat. Good luck to you both.
Also ask your doctors to run a FT-3 and FT-4 to confirm that you are converting your replacement properly.