Yes, I use the space heater for heating inside the chamber. It also has a fan built in so it really helps maintain even temps in there (at least best I can tell).
So you are going to have a freezer, and try to control the temp within the fridge section?
How do you plan to do it? These units only have one compressor, unless you are buying a high end sub zero or something. They work by cooling the freezer compartment and venting cold air to the fridge. So if your fridge section is at 60 degrees, the freezer will probably be pretty warm... Make sure you think it all through before dropping the cash. If you have any questions, fire away!