After looking at the picture of the thermostat, I would recommend against buying it. Like you said, it does not have a temperature 'probe'. It appears that the unit will turn on/off according to a temperature that can be set by the user, via the dial in the middle. However, it lacks an external probe. I believe this thermostat measures the temperature on the upper right side, where the slits are located. So it essentially only will measure the ambient temperature of where the unit is located (unless you can somehow cut the slits and extend the temperature probe/sensor beneath or place the thermostat inside of your viv, upsidedown, above the heat pad--which may not work because the cord of the heat pad plugs into that side, and I would not recommend doing this because of this electrical equipment being inside with your snake).
I personally use rheostats, which are cheaper when you only have a few setups. Here's what I use:
Dimmer/Rheostat
Basically plug your heat pad into this rheostat, then into the wall. The cord is long/extended so that the dimmer control has about 6' of reach from the wall plug. Then just use trial and error until you get the desired temperature of the heat pad using any thermometer (with probe). Occasionally, you may have to adjust it depending on your home's inside temperature, but not often. I pay about $10 for these in the store at Lowe's and Home Depot.
As far as elevating the tank/leaving room underneath, I do recommend this. This allows airflow and can prevent marring on some surfaces and preserves some heat pads from over heating. I do not think it is really needed, but better safe than sorry. Hope this helps.
