If you go to a 120V fridge, you'll have to either power it from the shore power connection or add an inverter and enough batteries to support the draw of the fridge. I have a 120V fridge and power it from a 1000W inverter and 300AH of batteries. I have a solar system that recharges the batteries. You'll have to do your homework to figure out how many AH's you'll need for the fridge and what types of inverter and batteries needed to accomplish that.
A ceiling fan is usually 120V in common parlance. Your light fixtures are 12V. Also, how will you secure the fan to the rafters and will they be big enough to support the weight? Added to the above, you will need to be very short people or the ceiling of your RV will need to be higher than typical to avoid injury. IMO, it's a very bad idea.