75 watt does seem like way too much if it's only 12-18 inches above the bottom of the enclosure. I'm only using a 65 watt on one end of my 55 gallon long,(18 inches high) and it's plenty enough to keep that end at around 85 degrees on the bottom, assuming the room is 70 degrees. I use a 60 watt for the 20 gallon tank (12 inches high) and it's actually a little more than enough.
That's one of the reasons I don't like enclosures taller than that. I don't want my snakes to have to climb for more heat, I don't want to burn more electricity, and I don't want to use a light bulb that gets super hot.
Even with your new bulb, you want to keep objects safely away from the bulb and don't make it easy for the snakes to climb up and get too close. In order to get a better idea of how heat is distributed, use a meat thermometer or other probe type and lay the probe on the bottom. That's where you should be getting 80-85 degree reading. Thermometers designed to take ambient air temperature can be very inaccurate if you're placing them directly under the light but they work well for the cool end of the enclosure.
From now on, I'll treat others like they treat me. Some will be glad, others should be scared
I use a dimmer on all of my bulbs and adjust heat accordingly. (A light dimmer from a hardware store works just as well and is much more affordable than a similar device purchased from a pet shop.) ;-)