As the PP said, your temps are not right. Conditions have to be proper or it is possible that he will refuse food.
To attain proper temps, you have to have a proper thermometer. The only good options are a digital thermometer with a PROBE or a temp gun. You can get a $12 accurite thermometer at walmart. To measure the temps PROPERLY with it, lay the probe on top of the hottest point, under the heat bulb, and leave it there for at least 45 minutes. These thermometers are great, because you can put the main part on the cool side for a good ambient temp reading.
As another poster said, too, remove the calcium sand immediately. It will be ingested and it is NOT digestible. It clumps up inside their bellies and can not be passed. It is dangerous.
Also, do not leave the crickets in with him. They can stress him out, but most of all, they will bite him and can leave sores.