Personally, I think, as you say your heartbeat is faster, maybe drop by 1/4 NDT and after two weeks if it is still faster reduce by another 25mcg and give NDT a longer try as it does look as if you benefit from it. It is the original form of thyroid hormone replacement, in use since 1892 (in different forms) and it contains T4, T3, T2, T1 and calcitonin (the latter three in small amounts). Calcitonin is good for strong bones.
These are a couple of excerpts from the above link (Dr Lowe was also an Adviser to Thyroiduk.org.uk and scientist and researcher and hated the way we are diagnosed/treated). He said the way we are now diagnosed is disgraceful (i.e. he and other doctors trained in the same era only took account of clinical symptoms and we got a prescription for NDT). Big pharma also wanted to make money and invented levothyroxine plus blood tests. I think that's why so many with clinical symptoms aren't diagnosed or undiagnosed or diagnosed with something else. New names, were Fibro, ME, and CFS.
Dr. Lowe: With most patients, I use thyroid function tests (TSH, free T3, and free T4) and thyroid antibodies only for a patient’s initial diagnosis. Afterward, I follow the practice, in principal, of Dr. Broda Barnes—that is, measuring tissue effects of particular dosages of thyroid hormone rather than remeasuring TSH, free T3, and free T4 levels.
My reason for this different protocol is simple: the TSH, free T3, and free T4 tell us only how the pituitary and thyroid glands are interacting. Of course, the test levels may also tell us something of the influence of thyroid hormone over the hypothalamus in its secretion of TRH, another hormone that influences the pituitary gland's secretion of TSH.
Many endocrinologists talk of using the TSH and thyroid hormone levels to "fine tune" hypothyroid patients’ thyroid hormone dosages. Considering how much the hormone levels vary, however, it’s obvious that the concept of fine tuning is mistaken. For the sake of their patients’ health, endocrinologists should promptly abandon the notion. This is unlikely, though, due to financial inducements the endocrinology specialty receives from corporations that profit from doctors endlessly ordering the hormone levels to "fine tune" their patients dosages. Hopefully, though, you can use the scientific evidence to persuade your doctor to use a safer and more effective approach with you. More on this topic.