You need a thermoSTAT to control the temps - they need to stay a constant temp throughout incubation. A thermoMETER does not control the amount of heat.
I don't believe the wet substrate shot up the temps, there's really no way to know.
A thermoSTAT is one of your MOST important investments for incubating eggs.
When mixing the perlite, it should be just barely moist. As in - you can barely feel that it's wet with the back of your hand when you mix it up.