I'm not sure why you're on such a high dose of methimazole, with a Free T4 of 1.07 when you've had RAI, which is intended to "kill" the thyroid; however, more important, why do you think it should be even an even higher dose?
High alkaline phosphatase can indicate, either a liver or bone problem; have any other test results been out of range or you had further tests done to determine if you have either one? Out of range bilirubin, AST and ALT are some tests that would indicate liver issues. Out of range phosphorus or calcium could indicate a bone problem.
What, if any, symptoms are you having?