Glad to hear that you have a good head on your shoulders. The good news is that you are not rushed to fix it right this very second or else something is going to get sick.
Did you put a thick blanket or towel over the enclosure other than the front? If you insulate the sides a little bit things should warm up, but not sure by how much. Some people will get another heater on a dimmer and put it on the cool side to up the temps. It is hard when you are in a larger room unless you 1. Use something else to add heat such as another heater or light, 2. Keep in the heat better by insulating, or 3. Just turn up the heat in your house.
Hopefully someone else pipes in here and has a suggestion about which might be better for this set up, and with those specific snakes.