You are going to need a thermostat to control the UTH. Your body temp is around 98 degrees, so if it feels warm to you it may be too hot for your snake. Since you said the temps drop into the low '70's at night it is very possible that he may try to get down to the glass for extra warmth and there is a high risk of him getting burned.
I don't know the dimensions of your tank, but if it is that tall then I'm not sure a heat lamp is going to do much good, plus, it will suck out your humidity even more. I would start by covering most of the top with something like aluminum foil, aluminum tape, or a piece of plexiglass. This will help keep the humidity in. If you don't already have one, you need to get a digital thermometer, preferably with a probe. You place the probe on top of the glass, under the substrate, over the UTH. This way you can keep track of the hottest temp you snake will come into contact with. I use the Acu-Rite Indoor/Outdoor Thermometer. One unit will tell you the warm side temp, ambient temp, and humidity. You can get them at some Wal-Marts in the Home Hardware section or at Lowes or Home Depot in the Outdoors section. They cost about $12 and look like this...
If you can't find one, another option is to get a temp gun. You can order them from places like ReptileBasics.com. You may also find them at stores that sell tools and also some auto parts stores sells them. If you have to go with the temp gun ,remember to push the substrate aside and shoot the temp on the glass directly over the UTH...
Congratulations on a successful first feeding...
