Hi Sharie,
It looks like you're probably in remission based on your lab results done while you were on 2.5 mg of mmi. Usually, it's best to first get the dose down to 1.25 mg and then have labs. But if your TSH was 5.5 on a 2.5 mg dose it's likely that you'd still be secreting TSH normally on a 1.25 mg dose.
A TSI test can be helpful in cases where TSH is still low. In your case the elevated TSH suggests that you no longer have troublesome levels of TSI because TSI would be suppressing the TSH level if TSI were present. The only exception would be if the 2.5 mg dose was way too high for you and it was causing hypothyroidism. Since you mention FT4 not being too low, it doesn't sound like this is the case.
A study several years ago showed that the TSH level is a good indicator of remission because normally in Graves' disease TSI cause the suppression of TSH. With TSH being produced and secreted at a good rate with only a low ATD dose, presumably TSI production has dramatically stopped. If you were to relapse block and replace would be a good alternative but I think you're in true remission. best, elaine