Husbandry issues & a rescue on the way..HELP please!

I'm going to be ordering some more UTH's & thermostats this week so I need some advice. I just can't seem to get my temps where they should be. Any advice would be so much appreciated! Here's what I got but I will be moving Kasmir to a 40 breeder in the next few days.

20L
2 UTH's (controlled w/dimmers) with accurite thermometers on glass under substrate, under each hide-temps fluctuate greatly for some reason. cool side temp taken w/temp gun on top of substrate is anywhere from 78-80ish. Temp on warm side is usually mid-upper 80's, early 90's. That is under the CHE..there is a UTH on that side as well, but that is not being used right now since the CHE warms that area about right. The reason I got the CHE is because I was having trouble with my ambient temp being too low. I'd like to know exactly what kind of thermostat i can get that will control both UTH's & the CHE. I understand the Herpistat 2 or the pro controls numerous devices but that is a bit more than I want to spend. Can i get 3 of the cheaper thermostats to run each one or does anyone have any other suggestions? I'm concerned I'll have the same problem with my ambient temp when I move to the 40 breeder. Thanks!

You are getting temp fluctuations because you are using dimmers. Once you get a thermostat, you won't have to deal with that.

The cheapest thermostat is the reptitemp 500r at about $25. It is not the best model but it gets the job done. I have been using one for almost 2 years now and it does its job :)

The reptitemp can only control 2 identical heat sources. So it can put two UTHs to the same temperature. You can put a dimmer in between one UTH and the thermostat to lower it for your cool side temperature. I would get a separate thermostat for the CHE or stop using it altogether.

The next step up would be a johnson controls or ranco thermostat from reptile basics. They are significantly more expensive but can control up to 6 identical devices to one temperature (unless you put a dimmer in line with one of the UTHs).

I have a reptitemp 500r for my boa's single setup and a johnsons controls for my rack setup. Both work very well.

Try covering the back and 2 sides with foam board. Sounds like the tank just isn't insulated enough for your room temps.
I second the suggestion that you NEED a thermostat, not just dimmers.

Have you started working on your humidity levels yet? With a CHE, that could prove to be an even bigger challenge. Low humidity dehydrates, which leads to bad sheds and respiratory issues.