Not sure how the pad could be getting to 165 on the outside of the tub and only 90 on the inside? Where are you checking the temp? If the temp of the pad on the outside is 165 then the inside surface would/should be the same, especially on a plastic tub. If the paper towels are browning/burning then I guarantee the surface temp is way more than 90!
Not sure if you saw the pics or not but I'm pointing the PE-1 directly at the bask spot about 1-2inches above it.
The room temperature is about 75-78F because I also keep Uroplatus and Rhacodactylus.