1. I would play with the set point on the t-stat. Raise and lower it to make sure the unit is cutting on and off and not just staying on.
2. Assuming it's working just play with the set point and measure the temp at the hot spot until you have it working at a desirable range.
For example if, when set at 88 the actual temp is 95, lower the set point to 83 or so and see is you end up around 90 on the actual temp.
3. For measuring actual temps, I'm hoping you're using something accurate. (IR Heat gun) But that's your call.
4. The main thing is just to make sure the t-stat is coming on and off. Then regardless of where your probe is situated you can compensate for differences between set point and actual temp.