I am older then you Auntie Megan, I had a hyst but kept ovaries, and used a 25 patch, I decided to use less and less estrogen and now get by with hardly any and feel very well, I never had intense flushes and none now.
The progynova you used was a "natural occurring" hormone estradiol valerate in a pill form. I don't know what your doctor has suggested but the fact that you have had a TIA means that it could preclude you from taking estrogen, if it had been me I would not touch estrogen again, even if it was suggested in a patch form.
Coming off estrogen abruptly may cause a backlash because your body has not gotten use to a lower level, and it may take time if you are lucky for the flushes to calm down.
Here is some info
http://www.nhs.uk/Conditions/Transient-ischaemic-attack/Pages/Prevention.aspx Depending on what you read estrogen theraphy either has no impact on stroke (very low risk) or can contribute along with other deciding factors.
There are other ways you can support your body post menopause if your doctor says no estrogen, have a google, but you must heed what your doctors tell you as far a TIA and Stroke are concerned.