Ambient temp as little to nothing to do with the hot spot and your UTH your cool and ambient temps depend on the temp in your home so if you cannot achieve 75 degrees min on the cool side you will need to either get your room temp up which is not very efficient for once snake, or supply with additional heat (can be a second heat pad with an additional thermostat set for the cool side)
Hopefully not inside the tank correct?We attached the probe to the bottom of the tank