That's reassuring ATB. I'm glad you've ruled out one variable & that the TFT has confirmed what thyroid replacement dose is right for you at this stage.
I consistently found over several trials with different doses of oestrogen, that Utro raises my heart rate uncomfortably, markedly disrupts the rhythm & makes me way too hot, wired & sleepless. A few other women have reported similar on here, but the majority seem to find it sedating, so it seems to be a very individual thing. I think perhaps because as hypothyroid women on thyroid replacement our homeostasis is already somewhat compromised, the body struggles more to adjust to other biochemical changes.
The palps & anxiety could well be a response to fluctuating oestrogen, as you say. I do find even long postmenopause that my body responds with palpitations to changes of HRT dose, either up or down, but also with changes of thyroid meds. It's all a learning process but with experience gets a bit easier to trust instinct. Keeping a close eye on your thyroid status as you have been, testing whenever you're not sure how things stand, should safeguard against being inadvertently on the wrong NDT dose for long, as you continue through the menopausal transition while symptoms may become confusing again.
I think you're doing remarkably well with your process of elimination. I hope things continue to be manageable for you & that you remain well. Good luck with the thyroid scan too.
Wx