Not necessarily a ceramic but a bulb is far superior to a mat when it comes to cresties. He won't be getting heat in the right way with a mat and it'll restrict his movement if he wants warmth.
Is that a picture of your setup? Because it looks like there is already a canopy?
The thermostat and thermometer probe would probably be best against the glass where the mat is to prevent it from getting too hot.
If you're able to, I would get a lot more cover in there (more vines, pieces of wood and plants). He'll appreciate extra cover.
CGD should be offered up higher as they are often reluctant to go to the floor. If he's going for the live food more than the CGD I would feed them to him maybe every other day, and keep the CGD in constantly. You'll need to feed the crickets different things, scraps of vegetable and fruit is perfect.