Well, treating your thyroid will improve your glucose tolerance, and it's possible that being slightly hyperthyroid was lowering your blood sugars even more because of the increased metabolism (I used to get positively hypoglycemic if I skipped a meal when I was hyperthyroid).
Now of course you will be coming down a little on your thyroid so watch those BS measurements carefully - you may not need to decrease your insulin.
BTW - I can relate to your story of being too hot at night - I used to throw the covers off and freeze my H when I was hyper (usually I'm cold in bed).
