Thanks! I have tried insulating the tank and it does seem to be helping a little. My temperatures are pretty consistent throughout the day. The only thing I'm struggling with a little now is night--in the morning when I get up and check it looks like temps drop a little on the hot side. Inside the hide is still 88F but the surrounding area on the hot side drops to 85-86. The cooler side drops about 5 degrees as well. Not sure if there's a trick to fixing this but I know nocturnal BP's aren't gonna like temp drops at night.
I will definitely get a glue gun for the sensor on the inside. I know normally it's frowned upon to keep them in the tank but as you said, I can't get an accurate reading of the actual temp otherwise. Fortunately, I had already set up the sensor for the heat pad as you described and that one works beautifully. It's just not quite enough for my cooler climate all on its own, more's the pity.