If your room temps get that hot or fluctuate a lot, a dimmer will not cut it. You really should get a thermostat to prevent heat spikes. If you don't you will find yourself adjust the dimmer every hour to compensate for the room temp change.
Trust me, your life will be so much easier after you get a thermostat.
Which thermostat do you recommend? Wouldn't it need 2 probes for both the hot & cool side inorder for it to know when to turn off & on?
For example, the Zoo-Med 500r only has 1 probe I believe. Can you set it to turn off when the probe is over 95F?