If your temps are getting up to 100 you really need to get some control on your heat sources. I think a UTH and a CHE is overkill, but maybe you need it for a tank that big, especially to keep your ambient temps up.
If you are not using it already, go to walmart and get an Acurite Indoor/Outdoor thermometer. It is about 12 bucks, and will measure one temp with a probe, which you put on the warm side bottom over the UTH, a put the unit on the cool side for humidity and cool side ambient temps. Aim for 92-94 on the warm and 82-84 on the cool. Also, you really should separate them soon, but if they are both small, you will probably want smaller enclosures for both of them, though you could try to just divide the tank you already have with another pane. They should have two identical hides, one warm, one cool as well. A cheap and easy way to control your heat is a lamp dimmer, about 10 bucks at Walmart, Home Depot, Lowes etc....just plug the dimmer into the socket, and the heat source into the dimmer. It will take more upkeep than a thermostat, but is a good cheap alternative until you can afford or are ready to buy a tstat.