Your kind of misunderstanding what this set up does.. You donhave a gradiant but not ambiant.. Your UTH should be 88-91 and your cool side (CHE) 76-81... Thats your Cool/Hot gradiant in this case...
If you decide to run a larger enclosure at some point, 48"x15"x12" (40G long) or a T8 PVC you can use one heat source, a RHP with a Herpstat portional tstat. That will be a Hot side of 90 and the other side (no heat source) will be around 76-80... Your not going to get that in a small tank using a CHE for ambiant and uth for basking spot .. your cool side is a bit to warm and thats why I was saying a 60 watt is ok for smaller tanks. I cant remember do you have a Jumpstart Tstat or what is controling the CHE? It needs to be turned down a bit..