If the glass almost burned your hand it WILL burn the snake.
A thermostat is a must have for the UTH and a probed thermometer is all you need to use for reading the temperatures.
Pet stores SUCK when it comes to helping you set up a ball python tank, they rarely know how to.
The dial thermometers are garbage and don't tell you the temperatures where you want to read them.
Pick up a t-stat for the belly heat so you little one doesn't suffer the consequences and get an indoor/outdoor thermometer with a probe.
The thermometer box goes in the cool end and the probe snakes it's way over to lay directly on the glass under the substrate so you know the hottest temperature the snake can get to.
Temps I shoot for:
78-80 cool end
86-87 warm end
90-92 hot spot

Sorry you had to be introduced into the hobby in this way, it's pretty common really, sad but common.